Etymology
1. c.1225, from O.Fr.
aise "comfort, pleasure," of unknown origin, despite attempts to link it to various L. verbs. The earliest senses in Fr. appear to be 1. "elbow-room" (from an 11th century Hebrew-French glossary) and 2. "opportunity." This led Sophus Bugge to suggest an origin in V.L.
asa, a shortened form of L.
ansa "handle," which could be used in the figurative sense of "opportunity, occasion," as well as being a possible synonym for "elbow," since L.
ansatus "furnished with handles" also was used to mean "having the arms akimbo." OED editors report this theory, and write, "This is not very satisfactory, but it does not appear that any equally plausible alternative has yet been proposed." The verb meaning "to give ease" is from 1340; the sense of "to relax one's efforts" is from 1863.
2. From Middle English ese, eise, aise, from Anglo-Norman ese (“ease”), from Old French eise, aise (“elbow room; opportunity”), of uncertain and obscure origin. Apparently related to Provençal ais, Italian agio and asio, Sicilian aciu and Portuguese azo. Sometimes ascribed to Vulgar Latin *āsia or *āsium, possibly from Latin ānsa (“handle, haft”) or Frankish *ansiju (“handle, loophole, eyelet; cup-handle; arms akimbo, elbow room”), but more often derived from Vulgar Latin *adjace(m), from Latin adjacēns (“adjacent, neighbouring”), present participle of adjaceō (“lie next to, border on”), though the forms and senses are difficult to trace clearly.
3. Alternatively, possibly from a non-Latin source such as Germanic or Celtic on the basis of the conflicting forms which appear in various Romance languages. Compare Old English īeþe (“easy”), Gothic 𐌰𐌶𐌴𐍄𐌹 (azēti, “ease; pleasure”), *𐌰𐌶𐌴𐍄𐍃 (*azēts, “easy”), Breton eaz, ez (“easy”), Irish adhais (“easy; leisure”). See also eath.
4. The verb is from Middle English esen, ultimately of the same origin. See: Middle English '
esen'.