A male Roman citizen typically had three names, a praenōmen, nōmen and cognōmen, i.e. a name which precedes (prae) the (family) name, the (family) name, and the name which comes with (cum) the (family) name. The praenōmen was used by family and close friends; in public contexts, the nōmen or cognōmen might be used, or both together. More formally, the father’s name and that of the tribe might be added: for example, M(arcus) Tullius M(arcī) f(īlius) Cor(nēliā tribū) Cicerō, Marcus Tullius Cicero, son of Marcus, from the Cornelian tribe.

At the end of the Republic, only 18 praenōmina were current, though 15 more are known from earlier times. Gaius, Lūcius, Marcus, Publius and Quintus were much the commonest and, conversely, others (marked with an asterisk) are found almost exclusively in only a few, mostly patrician, families:

A. Aulus Ap. Appius*
C. Gaius Cn. Gnaeus
D. Decimus K. Kaesō*
L. Lūcius M. Marcus
Mam. Māmercus* M’. Mānius*
N. Numerius* P. Publius
Q. Quintus Ser. Servius*
S(ex). Sextus Sp. Spurius*
T. Titus Ti. Tiberius

Roman praenōmina may seem very restricted to us, but a Roman would find our abbreviations peculiarly vague. Without further guidance, he could not fully identify M. Jordan, M. Monroe, M. Mouse or M. Proust, whereas M. Tullius Cicero is unambiguous.

The letter G was said to have been invented in the 3rd cent. BC as a modification of C, which continued to be used in the abbreviations for Gaius and Gnaeus. The invention is usually credited to one Carvilius, a freedman reported, rather improbably, to have been the first person to teach for a fee in Rome. (His former owner, the consular Sp. Carvilius Ruga Maximus, notoriously divorced his wife c. 230 BC on the grounds that she was sterile, and that he could not therefore assure the censors that he was married for the purpose of procreation.)

The nōmen denoted the family to which a person belonged. Nearly all nōmina end in -ius; for example, Tullius, Iūlius, Antōnius, Horātius, Ovidius, Propertius, Vergilius. A distinguished exception is Annaeus, the family name of the Senecas.

The origin of most nōmina is lost to us, but it seems reasonable to asume that Ovid’s ancestors were sheep-herders (ovis, -is fem. 3 “sheep”) in his native Abruzzi, an area in which sheep-farming is traditional; see Gabriele D’Annunzio’s famous poem, I Pastori. Ovid’s step-daughter married P. Suillius Rufus (“red-haired”), who became consul in AD 43 or 45; his family may have made their money from pigs (sūs, suis common 3 “pig”, and note also suīle, -is neut. 3 “pig-sty”). (Her other husband, Cornelius Fidus, once burst into tears in the senate when Domitius Corbulo, Nero’s great general, called him a “plucked ostrich” [strūthocamēlus dēpilātus], a choice spark of personal invective of the sort that may have led to many of the less complimentary cognōmina.) The same background in pig-farming can be surmised for the family of M. Porcius Cato.

Other such nōmina hinting at a family involvement in animal husbandry are Asinius (asinus, -i masc. 2 “donkey”; e.g. C. Asinius Pollio, an early patron of Vergil), Hirtius (hirtus, -i masc. 2 “billy-goat”; e.g. A. Hirtius, consul in 43 BC), Vitellius (vitellus, -i masc. 2 “calf”; e.g. A. Vitellius, emperor for several weeks in AD 69). cognōmina could start as whimsical nicknames. In Varro’s treatise on farming, the Dē Rē Rusticā, advice on care of the pig is given by Cn. Tremellius Scrofa (“Sow”). Varro enjoys rather obvious puns: cows are discussed by one Vaccius, aviaries by L. Cornelius Merula (“Blackbird”). Varro’s Scrofa, however, says explicitly: cognosce meam gentem suillum cognōmen nōn habēre, nec mē esse ab Eumaeō ortum “Know that my family does not have a piggy cognomen and that I am not a descendant of Eumaeus [Odysseus’ pig-man]”. He explains his cognōmen as having been awarded to his grandfather ex virtūte when, on campaign in Macedonia, he had made good a boast that he would scatter the enemy as a scrofa scatters her piglets. There is, however, another version: an early Tremellius had hidden a neighbor’s pig under the blankets of the bed in which his wife was sleeping, and, when the neighbor came to search for it, he swore that the only scrofa in the house was the one lying in the bed. In his speeches against C. Verres, Cicero puns repeatedly on verrēs (“boar”), but makes a laudatory reference to Scrofa as Cn. Tremellius. In the 2nd or 3rd century AD, one M. Porcius Aper served as a tribūnus mīlitum with the 6th legion.

Names which to us might seem odd, even humorous, often lose their literal force. Ovid refers to himself by name more often than does any other ancient poet, always as Nāsō “Nosey”; Helmut Kohl (“Cabbage”) was chancellor of [West] Germany for 16 years (and his nickname was Birne [“pear”]). There was another Naso, M. Actorius Naso, a 1st cent. BC historian twice cited by Suetonius in his Life of Julius Caesar.

The cognōmen specified the particular branch of the family to which a man belonged and, like the praenōmen, helped identify him as an individual. For example, the Cornelii had at least nine branches. By contrast to praenōmina, there was great variety in cognōmina. They could be derived from many sources, but the most notable are those given ex virtūte, indicating military achievement (e.g. P. Cornelius Scipio Africanus, the cognōmen Africānus being in honor of his victory over Hannibal at Zama in 202 BC) and those indicating adoption (e.g. P. Cornelius Scipio Aemilianus Africanus Numantinus, who took the full name of his adoptive father, the son of the victor of Zama, together with the cognōmen Aemiliānus, indicating his origins, as the son of L. Aemilius Paullus, the victor over Perseus of Macedon at Pydna in 168. [He himself assumed the honorific cognōmen Numantīnus after he put an end to resistance to Rome in Iberia by his taking of the small, but important, town of Numantia in 133]).

Some cognōmina are flattering, as, for example, Ap. Claudius Pulcher (“handsome”) or L. Cornelius Sulla Fēlix (“fortunate”). Others are distinctly not so: an ancestor of the poet P. Ovidius Nāsō presumably had a big nose; of the poet Q. Horatius Flaccus, floppy ears; of P. Quinctilius Vārus, the general who lost three legions in the Teutoburg disaster of AD 9, bandy legs.

No cognōmen was as evocative as Caesar. Some said that an early member of the family had been born by Caesarian section (caedō, -ere, cecīdī, caesum 3 “cut”; (the praenōmen Kaesō will have had the same origin), or that he had single-handedly killed an elephant in battle (casai being Moorish or caesa Punic for “elephant”), or that he had eyes of a remarkable grey-blue colour (caesius, -a, -um), or that he already had a full head of hair (caesariēs, caesariēī f. 5) at birth. Caesar may have been particularly pleased by this last explanation, for he himself was practically bald, a fact which he took pains to disguise by wearing a laurel wreath on all possible occasions. (The right to wear this wreath was said to have been the most gratifying of all the honors bestowed on him by the senate and people.) It has been suggested that the name is actually derived from the Etruscan city of Caere (in Etruscan Caesre).

There was no limit to the number of cognōmina an individual might possess, but no one else comes close to Q. Pompeius Senecio ... (etc., etc.) ... Sosius Priscus, consul in AD 169, who had 36, as is known from a commemorative inscription found at Tivoli. (That Iūlius is used three times, and Sīlius twice, will have made it that much easier for him to remember his name.)

Not all Romans had a cognōmen. For example, C. Marius, seven times consul and Julius Caesar’s uncle by marriage, Cn. Pompeius, until his army acclaimed him as Magnus in 81 BC, M. Antonius, the triumvir, T. Livius, the historian, A. Vitellius, emperor briefly in AD 69. (After Antony’s defeat by Octavian [Augustus], the Senate decreed that no Antonius should bear the praenōmen Marcus.) Certain types of cognōmina later became known as agnōmina (ad + nōmen; i.e. names added to the (family) name (and usually to other cognōmina).

Modern usage is generally to refer to less familiar figures by their nōmen and cognōmen. Certain famous persons are known by their nōmen (e.g. Lucretius, Propertius, Petronius) or by an Anglicized version of it (e.g. Vergil, Horace, Ovid), others by their cognōmen, either without change (e.g. Caesar, Catullus, Cicero) or with slight change (e.g. Catiline, Lucan, Martial).

praenōmina are almost never used: notable exceptions are made to distinguish between the Gracchi brothers and to denote Sextus Pompey, who saw his father butchered on the beach in Egypt after Pharsalus and continued the struggle against the 2nd triumvirate till the mid-30s. (Rather confusingly, he adopted the name Magnus Pompeius Magnī fīlius Pius.) The Anglicized form Mark Antony is probably influenced by Shakespeare.

The choice between the various combinations of praenōmina, nōmina and cognōmina seems arbitrary, but is adhered to fairly rigidly in individual cases: the playwright Terence (P. Terentius Afer) is never called Terentius or Afer or Terentius Afer, whereas the great scholar Varro (M. Terentius Varro) is never called Terence, though he is occasionally Terentius Varro; to refer to Ovid as Naso or to Vergil as Maro is antiquated; to call Cicero Tully has long gone out of fashion, while Sallust (C. Sallustius Crispus) has never been known as Crispy, and M. Porcius Cato has always been known as Cato.

The emperor Augustus had a particularly complex name. He was born as C. Octāvius. As a child, he was given the cognōmen Thūrīnus, either because his family was from Thurii (in S. Italy) or because his father had defeated remnants of the partisans of Spartacus and Catiline there. On his adoption by his great-uncle, Julius Caesar, he became C. Iūlius C. f(īlius) Caesar Octāviānus. He himself never used the cognōmen Octāviānus, though he was so called by his contemporaries, and he is still known as Octavian if reference is being made to the period of his life before 27 BC, when he became Augustus. He also dropped Iūlius, preferring to have the cognōmen Caesar as his nōmen. After the deification of Julius Caesar, he restyled his name to C. Caesar Dīvī f. (i.e. “son of a god”). He preferred to use the further cognōmen Imperātor in the place of his praenōmen. When the Senate gave him the title Augustus, his name reached its definitive version, Imperātor Caesar Dīvī f. Augustus.

One Greek source suggests that Augustus initially had the cognōmen Caepiās (perhaps from caepa, -ae fem. 1 “onion” [cf. e.g. Cicero from cicer, ciceris neut. 3 “chick-pea”, Pīsō from Pīsum, -ī neut. 2 “pea”]; Caepiō, presumably cognate, occurs quite frequently as a cognōmen, and was for a time the official nōmen of M. Junius Brutus, the most prominent of Caesar’s murderers).

Nothing illustrates the low status of women so vividly as the fact that they were usually known only by the feminine form of the family nomen (e.g. Tullia, Iūlia, Semprōnia), without even a praenōmen, except that Maior, Minor, Tertia, Quarta etc. would be used to distinguish between sisters. In the late Republic, it became more frequent for women to be known by the feminine form of the family nōmen and by the cognōmen in the genitive case; e.g. Tullia Cicerōnis. In modern Greece an unmarried woman’s surname is the family name in the genitive case, and most Slavic countries have a comparable system.

Women generally did not change their name when they married. Many married women referred to in inscriptions have the same name as their husbands, presumably because they had both been slaves in the same household, or because freedwomen had married their former owners. Cicero’s first wife was called Terentia; she seems to have lived to the age of 103, with subsequent marriages to the historian Sallust and to M. Valerius Messalla Corvinus. Messalla was not only a successful military commander, but an important patron of literature, a rival in this respect to C. Maecenas, whose wife was also called Terentia; it would be fascinating to know what relation, if any, there was between the two women.

Curious forms such as Gāipor, Lūcipor, Marcipor (= Gaiī puer, Lūciī puer, Marcī puer) attest that in early times slaves had little personal identity. Later, they had a single name, but their owner’s name might be appended, as e.g. Fēlix Antōniī (servus), “Felix, the slave of Antonius”. There was a broad range of slave names, a large proportion being Greek. (It would enhance a slave’s value to suggest an origin in such a civilized part of the Empire.) If a slave was freed, he typically took the praenōmen and nōmen of his ex-master, but retained his slave-name as his cognōmen. Herodes Atticus (who built the Odeon at Athens) called a group of his slaves by the names of the letters of the alphabet, which they wore on the back of their tunics to help his son to learn to read.