Where does “fuckweasel” come from?

fuckweasel (English) comes from English weasel, from Middle English wesele, from Old English weosule, from Proto-West Germanic wisulā, from Proto-Germanic wisulǭ, from Proto-Germanic wisō- — European polecat, "Mustela putorius".

Ancestry of “fuckweasel”, step by step

fuckweasel traces back through two separate lines of ancestry.

via English weasel

StepLanguageWordMeaning
1EnglishweaselThe least weasel, "Mustela nivalis"; Any of the...
2Middle Englishweseleweasel, polecat; A meal made of a pig or a capon...
3Old Englishweosuleweasel
4Proto-West Germanicwisulāweasel
5Proto-Germanicwisulǭweasel
6Proto-Germanicwisō-European polecat, "Mustela putorius"

via English fuck

StepLanguageWordMeaning
1EnglishfuckTo have sexual intercourse, to copulate; To have...
2Middle Englishfukkento fuck; to beat, strike
3Old Norsefukka
4Proto-Germanicfukkōnąto blow, gust; to strike, assail; to copulate
5Proto-Indo-Europeanpewǵ-to punch, fist-fight; to prick, poke, stab
Every word from Proto-Germanic wisō-Every word from Proto-Germanic wisulǭEvery word from Proto-West Germanic wisulā