sextillion (n.)

one more than five; twice three; the number which is one more than five; a symbol representing this number;" Old English siex, six, seox, sex, from Proto-Germanic *seks (source also of Old Saxon and Danish seks, Old Norse, Swedish, and Old Frisian sex, Middle Dutch sesse, Dutch zes, Old High German sehs, German sechs, Gothic saihs), from PIE *s(w)eks (source also of Sanskrit sas, Avestan kshvash, Persian shash, Greek hex, Latin sex, Old Church Slavonic sesti, Polish sześć, Russian shesti, Lithuanian šeši, Old Irish se, Welsh chwech).

As "playing card with six spots or pips" by 1590s. Six-footer "person measuring six feet or more" is by 1828. Six-shooter, usually a revolver with six chambers (firing six shots in succession), is attested from 1842; six-pack of beverage containers is from 1952, of abdominal muscles by 1995.

[Married] In Dana, [Mass.], on the 30th ult. by Ephraim Whipple, Esq. Mr. Jason W. Williams, M. D. to Miss Malinda Chamlin, of Dana,—a couple of six footers. Printers in New York, Ohio, Alabama, Vermont, Connecticut, Rhode-Island, New Hampshire and Maine, are requested to publish the same marriage, that his brothers and sisters may have due notice thereof and rejoice accordingly. [Burlington, Vt., Weekly Free Press, Feb. 8, 1828]

Six of one and half-a-dozen of the other "little difference" is recorded from 1833. Six-figure (adj.) in reference to hundreds of thousands (of dollars, etc.) is from 1840. Six feet under "dead" is from 1942.

The phrase at sixes and sevens originally was "hazarding all one's chances," first in Chaucer, perhaps from dicing (the original form was on six and seven); it could be a corruption of at cinque and sice "exposed to great risk" (1530s), literally "at five and six," using the French names (which were common in Middle English) for the highest numbers on the dice. The meaning "at odds, in disagreement or confusion" in the exact phrase is from 1785; in Middle English the phrase set at (or on) six and seven meant "play havoc, create an uproar."

"ten hundred thousand, a thousand thousands," late 14c., milioun, from Old French million (late 13c.), from Italian millione (now milione), literally "a great thousand," augmentative of mille "thousand," from Latin mille, which is of uncertain origin. From the start often used indefinitely for "a very great number or quantity."

In the West it was used mainly by mathematicians until 16c., but India, with its love of large numbers, had names before 3c. for numbers well beyond a billion. The ancient Greeks had no name for a number greater than ten thousand, the Romans for none higher than a hundred thousand. "A million" in Latin would have been decies centena milia, literally "ten hundred thousand." Million to one as a type of "long odds" is attested from 1761. Related: Millions.

1680s, from French billion (originally byllion in Chuquet's unpublished "Le Triparty en la Science des Nombres," 1484; copied by De la Roche, 1520); see bi- "two" + million. A million million in Britain and Germany (numeration by groups of sixes), which was the original sense; subsequently altered in French to "a thousand million" (numeration by groups of threes) and picked up in that form in U.S., "due in part to French influence after the Revolutionary War" [David E. Smith, "History of Mathematics," 1925]. France reverted to the original meaning in 1948. British usage is truer to the etymology, but U.S. sense is said to be increasingly common there in technical writing.

In Italian arithmetics from the last quarter of the fifteenth century the words bilione or duilione, trilione, quadrilione or quattrilione, quintilione, cinquilione, or quinquilione, sestione or sestilione, settilione, ottilione, noeilione and decilione occur as common abbreviations of due volte millioni, tre volte millione, etc. In other countries these words came into use much later, although one French writer, Nicolas Chuquet, mentions them as early as 1484, in a book not printed until 1881. The Italians had, besides, another system of numeration, proceeding by powers of a thousand. The French, who like other northern peoples, took most if not all their knowledge of modern or Arabic arithmetic from the Italians, early confounded the two systems of Italian numeration, counting in powers of a thousand, but adopting the names which properly belong to powers of a million. [Century Dictionary]

For a time in Britain gillion (1961), based on giga-, was tried as "a thousand million" to avoid ambiguity. Compare milliard.