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].
"capable of burning," 1520s, from French combustible, or directly from Late Latin combustibilis, from Latin combustus, past participle of combuere "to burn up, consume" (see combustion). Figurative sense "easily excited" is from 1640s. As a noun, "a substance that will burn," from 1680s. Related: Combustibility (late 15c.).
<a href="https://www.etymonline.com/word/non-combustible">Etymology of non-combustible by etymonline</a>
Harper, D. (n.d.). Etymology of non-combustible. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/non-combustible