demodulation (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-.

late 14c., modulacioun, "act of singing or making music, harmony," from Old French modulation "act of making music" (14c.) and directly from Latin modulationem (nominative modulatio) "rhythmical measure, singing and playing, melody," noun of action from past-participle stem of modulari "regulate, measure off properly, measure rhythmically; play, play upon," from modulus "small measure," diminutive of modus "measure, manner" (from PIE root *med- "take appropriate measures"). Meaning "act of regulating according to measure or proportion" is from 1530s. Musical sense of "action or process of changing from one key to another" is by 1690s.