"second self, counterpart," 1530s, a Latin phrase (used by Cicero), "a second self, a trusted friend" (compare Greek allos ego); see alter and ego.

c. 1200, "man lacking in self-restraint," from wild (adj.) + man (n.). From mid-13c. as "primitive, savage." Late 14c. as a surname.

Latin adverbial phrase, literally "by that very fact, by the fact itself," from neuter ablative of ipse "he, himself, self" + ablative of factum "fact" (see fact).

1905, from Irish, literally "we ourselves," from Old Irish féin "self," from PIE *swei-no-, suffixed form of root *s(w)e- (see idiom). The movement was founded 1905 by Irish journalist and politician Arthur Griffith (1872-1922).