A lot vs. Alot: 9 Grammatical Pitfalls
1530s, "not capable of sin," from Middle French impeccable (15c.) or directly from Late Latin impeccabilis "not liable to sin," from assimilated form of in- "not, opposite of" (see in- (1)) + pecare "to sin," of unknown origin. Meaning "faultless" is from 1610s. Related: Impeccably.