tranquility (n.)youdaoicibaDictYouDict[tranquility 词源字典]
also tranquillity, late 14c., from Old French tranquilite "peace, happiness" (12c.), from Latin tranquillitatem (nominative tranquillitas) "quietness, stillness; serenity," from tranquillus "quiet, calm, still," perhaps from trans- "over" (here in its intensive sense of "exceedingly") + a root possibly related to quies "rest" (see quiet (n.)).[tranquility etymology, tranquility origin, 英语词源]
lown (1)youdaoicibaDictYouDict
"A calm or quiet state; stillness, tranquillity", Middle English. Originally from early Scandinavian (compare Old Icelandic logn, Norwegian regional logn, Old Swedish lughn (Swedish lugn), Old Danish lun, lugn, loghn, lundh (early modern Danish luun, lowen, Danish lun, lune), all nouns in sense ‘calm, stillness, tranquillity’, and also Old Icelandic lygn (adjective) calm, Norwegian lun, (regional) logn, Old Swedish lughn (Swedish lugn, lygn), Danish lun, all adjectives in sense ‘still, calm’) from the same Germanic base as Old Icelandic lauss free, unencumbered.