U-turn (n.)

13c., "action of rotating; a revolution about an axis, movement about a center," also as a wrestling maneuver, from Anglo-French tourn (Old French torn, tour), from Latin tornus "turning lathe" (see turn (v.)); also partly from turn (v.).

From early 14c. as "a turning aside from one's course, deviation from one's path;" by early 15c. in a physical sense, "a turning into another or different way." The sense of "angle, curve, place of bending" (in a road, river, etc.) also is by early 15c.

By late 14c. as "a change in position so as to face in another direction," also "change in a state of affairs."

The sense of "act or deed" (as in good turn) is recorded from c. 1300. The meaning "an individual's time for action, when these go around in succession," is recorded from early 14c. (to take turns is from mid-14c.); specifically as "spell of work" from late 14c.

The meaning "beginning of a period of time" is attested from 1853 (as in turn-of-the-century, which is from 1921 as an adjectival phrase).

Phrase done to a turn (1780) suggests meat roasted on a spit. The turn of the screw (1796) is the additional twist to tighten its hold, sometimes with reference to torture by thumbscrews.

alphabetic character, in early writing not always distinguished from V and W; for historical evolution, see V. U-turn is attested by 1921, for the shape of the course described by the vehicle.

Attested punningly for you by 1588 ["Love's Labour's Lost," V.i.60], not long after the pronunciation shift that made the vowel a homonym of the pronoun. As a simple shorthand for you (without intentional word-play), it is recorded by 1862. In the old British movie classification code (1922) it stood for universal, as "suitable for all ages" (equivalent of American G).

Common in business names since 1923 (U-Haul is attested by 1950), earlier in newspaper advertisements (u haul is attested by 1937 in classified ads for large items or lots that must be picked up by the purchaser; while-u-wait for suit cleaning, etc., is by 1911.

The substitution of Middle English -o- for Old English -u- before -m-, -n-, or -r- was a French scribal habit before minims to avoid misreading the letters in the old style handwriting, which jammed them together. The practice transformed some, come, monk, tongue, and worm.