Expiration

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late Middle English (denoting a vapour or exhalation): from Latin exspiratio(n- ), from the verb exspirare (see expire).

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Borrowed from Middle French expiration, from Latin exspīrātiōnem, accusative singular of exspīrātiō.

etymonline

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expiration (n.)

early 15c., expiracioun, "vapor, breath," from Latin expirationem/exspirationem (nominative expiratio/exspiratio) "a breathing out, exhalation," noun of action from past-participle stem of expirare/exspirare "breathe out; breathe one's last" (see expire). Meaning "termination, end, close" is from 1560s.