jolly

From Middle English joli, jolif (“merry, cheerful”), from Old French joli, jolif (“merry, joyful”). For the loss of final -f in English, compare tardy, hasty, hussy, etc. It is uncertain whether the Old French word is from Old Norse jól ("a midwinter feast, Yule", hence "fest-ive"), in which case, equivalent to yule + -ive, compare Dutch jolig (“happy, festive, frolicsome, jolly”), West Frisian joelich, joalich (“merry, jolly”), Middle High German jœlich (“hooting, jubilant”). Alternatively, the Old French adjective has been conjectured to derive from a Vulgar Latin *gaudivus (from Latin gaudeō, more at joy), in which case it would require Early Old French ⟨d⟩ /ð/ to irregularly become ⟨l⟩ in jolif rather than being dropped, which is the usual case (alternatively, /l/ may be a hiatus filler inserted into expected *joïf). A possible parallel of ⟨d⟩ to ⟨l⟩ can be seen in the French name Valois, according to one hypothesis from Latin Vadensis, though this origin is itself uncertain and disputed.

来源：wiktionary