loathe: [OE] Loathe originated as a derivative of the adjective loath or loth [OE]. This originally meant ‘hostile’ or ‘loathsome’, and goes back to a prehistoric Germanic *laithaz, which also produced Swedish led ‘fed up’ and German leid ‘sorrow’, and was borrowed into the Romance languages, giving French laid and Italian laido ‘ugly’. [loathe etymology, loathe origin, 英语词源]
Old English laðian "to hate, to be disgusted with," from lað "hostile" (see loath). Cognate with Old Saxon lethon, Old Norse leiða. Related: Loathed; loathing.