depopulation 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-.

1610s, "whole number of inhabitants in a country, state, county, town, etc," from Late Latin populationem (nominative populatio) "a people; a multitude," as if from Latin populus "a people" (see people (n.)). From 1776 as "act or process of peopling" (a country, etc.). Population explosion "rapid or sudden increase in the size of a population" is attested by 1953.