"1 more than three, twice two; the number which is one more than three; a symbol representing this number;" Old English feower "four; four times," from Proto-Germanic *fedwores (source also of Old Saxon fiuwar, Old Frisian fiower, fiuwer, Frankish *fitter-, Dutch vier, Old High German fior, German vier, Old Norse fjorir, Danish fire, Swedish fyra, Gothic fidwor "four"), from PIE root *kwetwer- "four." The phonetic evolution of the Germanic forms has not been fully explained; Watkins explains the -f- as being from the following number (Modern English five).

To be on all fours is from 1719; earlier on all four (14c.). Four-letter word as a euphemism for one of the short words generally regarded as offensive or objectionable is attested from 1923; four-letter man is recorded from 1920 (apparently as a euphemism for a shit). Compare Latin homo trium litterarum, literally "three-letter man," a euphemism for fur "a thief." A four-in-hand (1793) was a carriage drawn by four horses driven by one person; in the sense of "loosely tied necktie" it is attested from 1892. To study The History of the Four Kings (1760, compare French Livres des Quatre Rois) contains an old euphemistic slang phrase for "a pack of cards," from the time when card-playing was considered a wicked pastime for students. Slang 4-1-1 "essential information" (by 1993) is from the telephone number called to get customer information. The four-color problem so called from 1879. The four-minute mile was attained 1954.

c. 1300, fourefoted; see four + foot (n.). Replacing forms from Old English feowerfote.

bedstead with high corner posts, 1836, from four + post (n.).

"person who wears glasses," slang, 1874; see four + eye (n.).

also foursquare, c. 1300, "having four equal sides," from four + square (adj.). As an adverb, in figurative use, "forthrightly, honestly" from 1845.

"cheat, dishonest person," 1900, from verb four-flush "to bluff a poker hand, claim a flush (n.) while holding only four cards in the suit" (1896).

old form of bowling, 1801, from four + corner (n.). So called because the four pins in it were set at the corners of a square.

"eight times eight; one more than sixty-three; a numeral representing this;" see sixty + four.

The phrase sixty-four dollar question "crucial question, most difficult question" is attested in general use from 1942, from the popular radio quiz show "Take It or Leave It" (debuted 1940), in which contestants answered questions of ascending difficulty and with ascending prizes for right answers, from $1 for the first to $64 for the seventh and last, and the option to take the winnings or take the next question. The show renamed itself "The $64 Question" in 1950. The amount of money offered advanced over time, and by 1955 it was "The $64,000 Question."

Baggy-browed Phil Baker took the $64 Question to Hollywood this week. As custodian of the renowned question—now so much a part of the national idiom that even $64 prose stylists avoid using it—and quizmaster of one of U.S. radio's most popular shows, Take It or Leave It (CBS, Sun., 10 p.m., E.W.T.), Phil Baker was ready to put both on celluloid. But there would be one slight variation: to suit Hollywood's philosophy, the $64 Question would become the $640 Question. [Time, March 6, 1944].

1976, translating Chinese sirenbang, the nickname given to the four leaders of the Cultural Revolution who took the fall in Communist China after the death of Mao.

of cars, 1957, from four + door.