Etymology
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smart money (n.)
"money bet by those in the know," 1926, from smart (adj.). The same phrase earlier meant "money paid to sailors, soldiers, workers, etc., who have been disabled while on the job" (1690s), from a noun derivative of smart (v.). Also "money paid to obtain the discharge of a recruit" (1760), hence "money paid to escape some unpleasant situation" (1818). Sometimes in legal use, "damages in excess of injury done."
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per diem 

1510s, "by the day, in each day," Latin, "by the day," from per (see per) + diem, accusative singular of dies "day" (from PIE root *dyeu- "to shine"). As a noun from 1809, "amount or allowance of so much every day."

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big deal (n.)
from 1860s as "a good deal, a large amount;" by 1878 in financial speculation, originally in California publications; see deal (n.1). As an ironic expression, popular in American English from c. 1965, perhaps a translated Yiddishism (such as a groyser kunst).
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legem pone (n.)
"payment of money, cash down," 1570s, old slang, from the title in the Anglican prayer-book of the psalm appointed for Matins on the 25th of the month; it was consequently associated especially with March 25, the new year of the old calendar and a quarter day, when payments and debts came due and money changed hands generally. The title is from the first two words of the fifth division of Psalm cxix: Legem pone mihi, Domine, viam justificationum tuarum "Teach me, O Lord, the way of thy statutes."
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cold feet (n.)

1893, American English, in the figurative sense "fear or doubt that reverses an intention to do something;" the presumed Italian original (avegh minga frecc i pee) is a Lombard proverb meaning "to have no money," but some of the earliest English usages refer to gamblers, so a connection is possible.

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whole nine yards (n.)
by 1970, of unknown origin; perhaps arbitrary (see cloud nine). Among the guesses that have been made without real evidence: concrete mixer trucks were said to have dispensed in this amount. Or the yard might be the word used in the slang sense of "one hundred dollars." Several similar phrases meaning "everything" arose in the 1940s (whole ball of wax, which is likewise of obscure origin, whole schmear); older examples include whole hog (see hog (n.)) and whole shooting match (1896); whole shebang (1895).
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