defecation 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-.

also faeces, c. 1400, "dregs," from Latin faeces "sediment, dregs," plural of faex (genitive faecis) "grounds, sediment, wine-lees, dregs," which is of unknown origin. Specific sense of "human excrement" is from 1630s in English but is not found in classical Latin. Hence Latin faex populi "the dregs of the people; the lowest of society."