Origin and history of detour

Middle English turnen, from late Old English turnian "rotate, revolve; move about an axis, center, or fixed position," also in part from Old French torner, tornier, Anglo-French turner "turn away or around; draw aside, cause to turn; change, transform; turn on a lathe" (Modern French tourner).

All are from Latin tornare "to polish, round off, fashion, turn on a lathe," from tornus "lathe," from Greek tornos "lathe, tool for drawing circles" (reconstructed in Watkins to be from PIE root *tere- (1) "to rub, turn").

From late 12c. as "change position or orientation so as to face or point in a different direction," hence "change course, go in a different direction." In reference to the tide, etc., "reverse course or direction," c. 1300.

Transitive senses in English are from c. 1200 as "cause to shift so as to face in a different direction;" by c. 1300 as "cause a change of course." Related: Turned; turning.

Many figurative senses and expressions (turn (something) into (something else)) likely grew from the notion of "shape (something) while rotating it on a lathe or wheel, form or fashion (a piece of wood or metal) with a chisel while the object is rotated," the classical sense, attested in English by mid-14c. "Execute in round outlines," hence "form, fashion, or shape in any way" (1610s).

From late 12c. as "cause to undergo transmutation from one substance to another." Hence "change in a character or property" (color, thickness, mass, etc.), c. 1300, also transitive. The sense of "become sour or tainted" is by 1570s.

Also from late 12c. as "lead to" (grief, advantage, etc.), "result as a consequence of;" from c. 1200 as "come to pass, happen, occur." Also from c, 1200 as "become inverted, assume a reverse or contrary position;" also "repel" (evil, danger); "rout in battle." By c. 1300 as "shift allegiance, shift loyalties, change sides," also transitive.

To turn down (v.) "reject" is recorded by 1891, American English. To turn in "go to bed" is attested from 1690s, originally nautical. Turn to "look to for help or hope, have recourse" is from late 14c. 

To turn the stomach "nauseate" is recorded from 1620s. To turn (something) loose "set free" is recorded from 1590s. To turn up one's nose as an expression of contempt is attested from 1779.

word-forming element of Latin origin meaning 1. "lack of, not" (as in dishonest); 2. "opposite of, do the opposite of" (as in disallow); 3. "apart, away" (as in discard), from Old French des- or directly from Latin dis- "apart, asunder, in a different direction, between," figuratively "not, un-," also "exceedingly, utterly." Assimilated as dif- before -f- and to di- before most voiced consonants.

The Latin prefix is from PIE *dis- "apart, asunder" (source also of Old English te-, Old Saxon ti-, Old High German ze-, German zer-). The PIE root is a secondary form of *dwis- and thus is related to Latin bis "twice" (originally *dvis) and to duo, on notion of "two ways, in twain" (hence "apart, asunder").

In classical Latin, dis- paralleled de- and had much the same meaning, but in Late Latin dis- came to be the favored form and this passed into Old French as des-, the form used for compound words formed in Old French, where it increasingly had a privative sense ("not"). In English, many of these words eventually were altered back to dis-, while in French many have been altered back to de-. The usual confusion prevails.

As a living prefix in English, it reverses or negatives what it is affixed to. Sometimes, as in Italian, it is reduced to s- (as in spend, splay, sport, sdain for disdain, and the surnames Spencer and Spence).

*terə-, Proto-Indo-European root meaning "to rub, turn," with derivatives referring to twisting, also to boring, drilling, piercing; and to the rubbing of cereal grain to remove the husks, and thus to threshing.

It might form all or part of: atresia; attorn; attorney; attrition; contour; contrite; detour; detriment; diatribe; drill (v.) "bore a hole;" lithotripsy; return; septentrion; thrash; thread; thresh; throw; threshold; trauma; trepan; tribadism; tribology; tribulation; trite; triticale; triturate; trout; trypsin; tryptophan; turn.

It might also be the source of: Sanskrit turah "wounded, hurt;" Greek teirein "to rub, rub away;" Latin terere "to rub, thresh, grind, wear away," tornus "turning lathe;" Old Church Slavonic tiro "to rub;" Lithuanian trinu, trinti "to rub," Old Irish tarathar "borer," Welsh taraw "to strike."