Inexcusable

wiktionary

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From Middle French inexcusable, from Latin inexcusabilis

etymonline

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inexcusable (adj.)

early 15c., from Latin inexcusabilis "without excuse; affording no excuse," from in- "not, opposite of" (see in- (1)) + excusabilis, from excusare "apologize, make an excuse for" (see excuse (v.)). Related: Inexcusably.