early 15c., from M.Fr. expirer, from L. expirare "breathe out, breathe one's last, die," from ex- "out" + spirare "to breathe" (see spirit
). "Die" is the older sense in English; that of "breathe out" is first attested 1580s. Of laws, patents, treaties, etc., late 15c. Related: Expired; expiring.