non-combatant n.

a prefix used freely in English and meaning "not, lack of," or "sham," giving a negative sense to any word, 14c., from Anglo-French noun-, from Old French non-, from Latin non "not, by no means, not at all, not a," from Old Latin noenum "not one" (*ne oinom, from PIE root *ne- "not" + PIE root *oi-no- "one, unique"). In some cases perhaps from Middle English non "not" (adj.), from Old English nan (see not). "It differs from un- in that it denotes mere negation or absence of the thing or quality, while un- often denotes the opposite of the thing or quality" [Century Dictionary].

mid-15c. (adj.) "contending, disposed to combat;" late 15c. (n.) "one who engages in battle;" from Old French combatant (Modern French combattant) "skilled at fighting, warlike" (also used as a noun in Old French), present-participle adjective of combattre (see combat (v.)).