demote 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-.

late 14c., promoten, "to advance (someone) to a higher grade or office, exalt or raise to a higher post or position," from Old French promoter and directly from Latin promotus, past participle of promovere "move forward, advance; cause to advance, push onward; bring to light, reveal," from pro "forward" (see pro-) + movere "to move" (from PIE root *meue- "to push away").

General sense of "to further the growth or progress of (anything)" is from early 15c. In late Middle English and early Modern English also promove, from the Latin verb. Related: Promoted; promoting.

"act or fact of being reduced to a lower rank or class," 1890, noun of action from demote (v.).