From Old Occitan [Term?] (compare Occitan fèl), from Latin fel (“bile”) (compare French fiel, Spanish hiel), from Proto-Indo-European *ǵʰelh₃- (“green”).
From Middle Dutch fel, from Old French fel.
From Proto-Indo-European *ǵʰelh₃- (“green”). The change from *ǵʰ- to f-instead of *h- De Vaan considers to be dialectal. Alternatively, the etymon *bʰel-, *bʰl̥H- (“yellow”). Cognates include bilis, holus and helvus; Ancient Greek χολή (kholḗ, “bile”) and χλωρός (khlōrós, “green”); and English yellow and gold.
Borrowed from Old French fel.
Proto-Germanic *faluz, cognate with felon.
From Old Portuguese fel, from Latin fel, from Proto-Indo-European *ǵʰelh₃- (“green”).
Borrowed from Hungarian -féle.
See Norwegian feil and Danish fejl. Used in Swedish at least since 1527. For the adverb, the now obsolete form felt was the dominating written form until the mid 19th century.
Cognate with Breton evel.
From Old Norse *fél, from Proto-Germanic *finhlō (“file”).