autoclave n.

word-forming element meaning "self, one's own, by oneself, of oneself" (and especially, from 1895, "automobile"), from Greek autos, reflexive pronoun, "self, same," which is of unknown origin. It also was a common word-forming element in ancient Greek, as in modern English, but very few of the old words have survived the interval. In Greek, as a word-forming element, auto- had the sense of "self, one's own, of oneself ('independently'); of itself ('natural, native, not made'); just exactly; together with." Before a vowel, it became aut-; before an aspirate, auth-. In Greek it also was used as a prefix to proper names, as in automelinna "Melinna herself." The opposite prefix would be allo-.

also *kleu-, klēu-, Proto-Indo-European root meaning "hook, crook," also "crooked or forked branch" (used as a bar or bolt in primitive structures). 

It forms all or part of: anschluss; autoclave; clause;  claustrophobia; claves; clavichord; clavicle; clavier; claviger; clechy; clef; cloison; cloisonne; cloister; close (v.); close (adj.); closet; closure; cloture; clove (n.1) "dried flowerbud of a certain tropical tree, used as a spice;" cloy; conclave; conclude; disclose; enclave; enclose; exclude; foreclose; include; occlude; preclude; recluse; seclude; slot (n.2) "bar or bolt used to fasten a door, window, etc." 

It is the hypothetical source of/evidence for its existence is provided by: Greek kleis "bar, bolt, key; collarbone," klobos "cage;" Latin clavis "key," clavus "nail," claudere "to shut, close;" Lithuanian kliūti "to catch, be caught on," kliaudžiu, kliausti "to check, hinder," kliūvu, kliūti "to clasp, hang;" Old Church Slavonic ključi "hook, key," ključiti "shut;" Old Irish clo "nail," Middle Irish clithar "hedge, fence;" Old High German sliozan "shut," German schließen "to shut," Schlüssel "key."