ease (n.)youdaoicibaDictYouDict[ease 词源字典]
c. 1200, "physical comfort, undisturbed state of the body; tranquility, peace of mind," from Old French aise "comfort, pleasure, well-being; opportunity," which is of unknown origin, despite attempts to link it to various Latin verbs; perhaps Celtic. According to OED, the earliest senses in French 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 Vulgar Latin asa, a shortened form of Latin ansa "handle," which could be used in the figurative sense of "opportunity, occasion," as well as being a possible synonym for "elbow," because Latin ansatus "furnished with handles" also was used to mean "having the arms akimbo." OED editors add, "This is not very satisfactory, but it does not appear that any equally plausible alternative has yet been proposed."

At ease "at rest, at peace, in comfort" is from late 14c.; as a military order (1802) the word denotes "freedom from stiffness or formality."[ease etymology, ease origin, 英语词源]
peace (n.)youdaoicibaDictYouDict
mid-12c., "freedom from civil disorder," from Anglo-French pes, Old French pais "peace, reconciliation, silence, permission" (11c., Modern French paix), from Latin pacem (nominative pax) "compact, agreement, treaty of peace, tranquility, absence of war" (source of Provençal patz, Spanish paz, Italian pace), from PIE *pag-/*pak- "fasten," related to pacisci "to covenant or agree" (see pact).

Replaced Old English frið, also sibb, which also meant "happiness." Modern spelling is 1500s, reflecting vowel shift. Sense in peace of mind is from c. 1200. Used in various greetings from c. 1300, from Biblical Latin pax, Greek eirene, which were used by translators to render Hebrew shalom, properly "safety, welfare, prosperity."

Sense of "quiet" is attested by 1300; meaning "absence or cessation of war or hostility" is attested from c. 1300. As a type of hybrid tea rose (developed 1939 in France by François Meilland), so called from 1944. Native American peace pipe is first recorded 1760. Peace-officer attested from 1714. Peace offering is from 1530s. Phrase peace with honor first recorded 1607 (in "Coriolanus"). The U.S. Peace Corps was set up March 1, 1962. Peace sign, both the hand gesture and the graphic, attested from 1968.