Meaning

noun a defense of some offensive behavior or some failure to keep a promise etc.

noun a note explaining an absence

noun a poor example

originFrom Middle English excusen (verb) and excuse (noun), borrowed from Old French escuser (verb) and excuse (noun), from Latin excūsō, excūsāre (“to excuse, allege in excuse, literally, free from a charge”), from ex (“out”) + causa (“a charge”); see cause, accuse and recuse. Displaced native Old English lād (“an excuse”) and lādian (“to excuse”).

Etymology from Wiktionary, CC BY-SA 3.0