1770, "estimated by averaging," from average (n.). By 1803 as "equal in amount to the sum of all particular quantities divided by the number of them," hence "of medium character."
1610s, "special messenger," from express (adj.). Sense of "business or system for sending money or parcels" is by 1794.
also moola, "money," c. 1920, American English slang, of unknown origin. Earlier it was a form of the Islamic title mullah.
1769, "to amount to," from average (n.). By 1831 as "find the arithmetical mean of unequal quantities;" 1914 as "divide among a number proportionately" (usually with out). Related: Averaged; averaging.
c. 1200, o cros, "in the shape of a cross;" c. 1300, a-croiz, "in a crossed position;" early 14c., acros, "from one side to another;" a contraction of Anglo-French an cros, literally "on cross;" see a- (1) + cross (n.)).
Meaning "on the other side (as a result of crossing)" is from 1750. In crossword puzzle clues from 1924. Spelling acrost, representing a dialectal or vulgar pronunciation, is attested by 1759. Phrase across the board "embracing all categories" (1945) is said to be originally from horse-racing, in reference to a bet of the same amount of money on a horse to win, place, or show. To get (something) across "make (something) understood or appreciated" is by 1913, probably from earlier theater expression get (something) across the footlights, perform it so as to be received by the audience (1894).
"to put up bail money," 1781, from one of the nouns post, but which one is uncertain. Related: Posted; posting.