Irritable

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mid 17th century: from Latin irritabilis, from the verb irritare (see irritate).

wiktionary

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Borrowed from French irritable, from Latin irritabilis

etymonline

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irritable (adj.)

1660s, "susceptible to mental irritation," from French irritable and directly from Latin irritabilis "easily excited," from irritare "excite, provoke" (see irritate). Meaning "responding quickly to a stimulus" is from 1791. Related: Irritably.