The Roman monetary system was based on three coins, the copper as and the silver sestertius and dēnārius. As their names indicate, the sestertius was originally worth two and a half assēs (sēmi + tertius, i.e. [two assēs and] half of a third as), the dēnārius ten assēs. Large sums of money were normally reckoned in sestertiī. The abbreviation for sestertiī was HS, derived from II (i.e two assēs) and S (sēmis [apparently sēmi + as]). A line above the letters denoting a number indicated thousands, and either a further line above HS as well or vertical lines before and after the number-letters indicated millions.
The Latin for “money” is pecūnia, -ae fem. 1, derived from pecus, -oris neut. and pecus pecudis fem., both meaning “herd of livestock”. Our word “fee” has a similar origin in the rural economy, being cognate with the Germanic Vieh (“cattle”), which is itself related to pecus. The late Latin capitāle, -is (from caput, capitis neut. 3 “head”) is the origin not only of “[financial] capital” but also of “chattel” and “cattle”.
The modern German word for “money”, Geld, is a variant on “gold”, which is so called because it is yellow (gelb). The French term argent is similarly derived, from argentum, -ī neut. 2 “silver”. The Spanish dinero and Portuguese dinheiro are derived from dēnārius, as also is the abbreviation d. used for the penny (cf. German Pfennig) in the old British system. Italian soldi and the abbreviation s. for the old British shilling are derived from the solidus (i.e. solidus nummus [“solid coin”]), a gold coin of the empire, originally worth 25 dēnāriī. (“Numismatics”, the study of coins, is derived from νόμισμα [nomisma], the Greek word for “coin”, under the influence of this Latin cognate term.) The abbreviation £ for the British pound is for libra pondō, i.e. a coin which was “a pound in weight”, the lines being added to the letter l to indicate the abbreviation. (The $ sign is an abbreviation of ps [= peso (literally “weight”)], and the Japanese ¥ [for Yen] is by analogy to £ and $.) “Salary” is from salārium, -ī neut. 2, a payment made originally to enable the recipient, esp. army officers and high-ranking government officials, to buy salt (sal, salis masc. [occasionally neuter] 3); hence “to be worth one’s salt”. “Stipend” is from stīpendium, -ī neut. 2, the weighing out (pendō, -ere, pependī, pensum 3) of small coins (stips, stipis fem. 3), originally in payment to soldiers. “Payment” is derived from pācō 1 “pacify (sc. one’s creditor)”. “Money” itself is derived from Monēta, a cult-name of Juno, who warns (moneō, -ēre, monuī, monitum 2) against counterfeiting. Roman money was coined primarily in the temple of Juno Moneta, hence our term “mint”. “Coins” are so called from the wedge (cuneus, -ī masc. 2) -shaped stamps with which they were produced.