defrock v.

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-.

mid-14c., from Old French froc "a monk's habit; clothing, dress" (12c.), which is of unknown origin; perhaps from Frankish *hrok or some other Germanic source (compare Old High German hroc "mantle, coat;" Old Norse rokkr, Old English rocc, Old Frisian rokk, German Rock "a coat, over-garment"). Another theory traces it to an alteration of Medieval Latin floccus, from Latin floccus "tuft of wool," a word of unknown origin. Meaning "outer garment for women or children" is from 1530s. Frock-coat attested by 1819.