livelong (adj.)youdaoicibaDictYouDict[livelong 词源字典]
also live-long, c. 1400, lefe longe (day), from leve, lief "dear" (see lief), used here as an emotional intensive + long (adj). From late 16c. conformed in spelling to live (v.) as lief grew strange. German has cognate die liebe lange Nacht, literally "the dear long night."[livelong etymology, livelong origin, 英语词源]