Origin and history of detail

"one who makes the outer garments of men and other garments of heavy stuff," late 13c., tailloir (late 12c. as a surname), from Anglo-French tailour, Old French tailleor "tailor," also "stone-mason" (13c., Modern French tailleur), literally "a cutter," from tailler "to cut," from Late Latin or old Medieval Latin taliare "to split" (compare Medieval Latin taliator vestium "a cutter of clothes"), from Latin talea "a slender stick, rod, staff; a cutting, twig."

Although historically the tailor is the cutter, in the trade the 'tailor' is the man who sews or makes up what the 'cutter' has shaped. [OED, 2nd ed., 1989]

The post-Latin sense development would be "piece of a plant cut for grafting," hence a verb, "cut a shoot," then, generally, "to cut." It had been connected with Sanskrit talah "wine palm," Old Lithuanian talokas "a young girl," Greek talis "a marriageable girl" (for sense, compare slip of a girl, twiggy), Etruscan Tholna, name of the goddess of youth. But de Vaan (2008) writes, "There is no viable etymology for talea, unless it is a derivative of talus 'ankle, knuckle'." An Old English word for a tailor was seamere, from seam (n.).

active word-forming element in English and in many verbs inherited from French and Latin, from Latin de "down, down from, from, off; concerning" (see de), also used as a prefix in Latin, usually meaning "down, off, away, from among, down from," but also "down to the bottom, totally" hence "completely" (intensive or completive), which is its sense in many English words.

As a Latin prefix it also had the function of undoing or reversing a verb's action, and hence it came to be used as a pure privative — "not, do the opposite of, undo" — which is its primary function as a living prefix in English, as in defrost (1895), defuse (1943), de-escalate (1964), etc. In some cases, a reduced form of dis-.