screwball n.

"cylinder of wood or metal with a spiral ridge (the thread) round it," c. 1400, scrue, from Old Frenchescröe, escroue "nut, cylindrical socket, screw-hole," a word of uncertain etymology; not found in other Romanic languages.

Perhaps via Gallo-Roman *scroba or West Germanic *scruva from Vulgar Latin scrobis "screw-head groove," in classical Latin "ditch, trench," also "vagina" (Diez, though OED finds this "phonologically impossible"). OED Seems to lean toward a group of apparently cognate Germanic words (Middle Low German, Middle Dutch schruve, Dutch schroef, German Schraube, Swedish skrufva "screw"), but these are said elsewhere to be French loan-words.

Kluge, Watkins and others trace it to Latin scrofa "breeding sow," perhaps on some fancied resemblance of the holes or furrows left by a rooting swine (compare Portuguese porca, Spanish perca "a female screw," from Latin porca "sow"). Latin scrofa in the "sow" sense is a specific Medieval Latin use; the word is literally "digger, rooter" (from PIE root *sker- (1) "to cut"). 

Originally an apparatus for lifting weight or pressing with it, hence its later consideration as one of the mechanical powers. The meaning "metal pin or tapered bolt with a spiral ridge, used to join articles of wood or metal," is by 1620s (specifically as wood-screw by 1841). The meaning "a twist or turn to one side" is by 1709.

The sense of "means of pressure or coercion" is from 1640s, often the screws, probably in reference to instruments of torture (as in thumbscrews). Meaning "prison guard, warder" is by 1812 in underworld slang, originally in reference to the key they carried (screw as slang for "key" is attested by 1795). In student slang, "professor or tutor who requires students to work hard" (1851).

The meaning "metal instrument with a winding or spiral shape or motion, used to draw corks from bottles" is by 1650s. As short for screw-propeller, by 1838. The sense of "small portion (of a commodity) wrapped up in a twist of paper" is by 1836. The British slang sense of "salary, wages: is by 1858, but the notion in it is obscure. The slang meaning "an act of copulation" is recorded from 1929 (canting sense of "a prostitute" is attested from 1725). Slang phrase have a screw loose "have a dangerous (usually mental) weakness" is recorded from 1810.

"round object, compact spherical body," also "a ball used in a game," c. 1200, probably from an unrecorded Old English *beal, *beall (evidenced by the diminutive bealluc "testicle"), or from cognate Old Norse bollr "ball," from Proto-Germanic *balluz (source also of Dutch bal, Flemish bal, Old High German ballo, German Ball), from PIE root *bhel- (2) "to blow, swell."

The meaning "testicle" is from early 14c. (compare ballocks). Ball of the foot is from mid-14c. The meaning "rounded missile used in warfare" is from late 14c.

The meaning "a game played with a ball" is from mid-14c. The baseball sense of "pitch that does not cross the plate within the strike zone" is by 1889, probably short for high ball, low ball, etc.

Ball-point pen is by 1946. Ball of fire when first recorded in 1821 referred to "a glass of brandy;" as "spectacularly successful striver" it is attested from c. 1900. Many phrases are from sports: To have the ball "hold the advantage" is from c. 1400. To be on the ball is from 1912; to keep (one's) eye on the ball in the figurative sense is by 1907, probably ultimately on golf, where it was oft-repeated advice. Figurative use of ball in (someone's) court is by 1956, from tennis.

The head must necessarily be steady, for it is most important that you should keep your eye fixedly on the ball from the moment that the club-head is lifted from the ground until the ball is actually struck. "Keep your eye on the ball," should be your companion text to "Slow back." [Horace G. Hutchinson, "Hints on the Game of Golf," 1886]

Once a meeting is over, someone will be expected to do something. Make sure it is someone else. This is known as keeping the ball in their court. [Shepherd Mead, "How to Get Rich in TV Without Really Trying," 1956]