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"testicles," early 14c., from plural of ball (n.1). See also ballocks. Meaning "courage, nerve" is from 1928. Balls to the wall, however, probably is from World War II Air Forces slang, from the ball that topped the aircraft throttle, thrust to the bulkhead of the cockpit to attain full speed. Ball-busting "difficult" is first recorded 1944; ball-buster, disparaging for "dominant female," is from 1974.
"round object," Old English *beal, from or corresponding to Old Norse bollr "ball," from Proto-Germanic *balluz (cf. Old High German ballo, German Ball), from PIE root *bhel- (2) "to blow, inflate, swell" (see bole).
Meaning "testicle" is from early 14c. Ball of the foot is from mid-14c. A ball as an object in a sports game is recorded from c.1200; To have the ball "hold the advantage" is from c.1400. To be on the ball is 1912, from sports. Ball-point pen first recorded 1946. Ball of fire when first recorded in 1821 referred to "a glass of brandy;" as "spectacularly successful striver" it is c.1900.
"dancing party," 1630s, from French, from Old French baller "to dance," from Late Latin ballare "to dance," from Greek ballizein "to dance, jump about" (see ballistics). Hence, "very enjoyable time," 1945, American English slang, perhaps back to 1930s in black slang.
A spherical object or mass.
A large pill or bolus.
blue balls, bust one's ass, the cat's meow, does howdy doody have wooden balls, cold enough to freeze the balls off a brass monkey, gripe one's ass, have brass balls, have someone by the balls, have the world by the balls, not get one's balls in an uproar, put balls on
ball up, beanball, butterfly ball, cannonball, carry the load, fireball, forkball, foul ball, get on the ball, go for the long ball, goofball, gopher ball, greaseball, greedball, have a ball, junk-ball, keep one's eye on the ball, meatball, not get one's balls in an uproar, nutball, oddball, on the ball, play ball, play catch-up, sleazebag, slimebag, softball, sourball, that's the way the ball bounces