What is the origin of guerdon?

Guerdon “a reward, recompense, or requital” is a variation of Old French werdoun, continuing a trend in which the w in Germanic-origin borrowings often becomes gu when adapted into French and other Romance languages. For other examples, compare the cognate pairs ward and guard, warranty and guarantee, and William and Guillaume. Old French werdoun comes from Medieval Latin widerdonum, which in turn was adapted from Old High German widarlōn, with a phonetic change from l to d because of the influence of Latin dōnum “gift.” Widarlōn is a compound of widar “again, back” (which survives today in the German expression auf Wiedersehen “until we meet again”) and lōn “reward” (cognate to Latin lucrum “gain, profit,” as in English lucrative). Guerdon was first recorded in English in the mid-14th century.