fell (v.1)

Old English fællan (Mercian), fyllan (West Saxon) "make fall, cause to fall," also "strike down, demolish, kill," from Proto-Germanic *falljanan "strike down, cause to fall" (source also of Old Frisian falla, Old Saxon fellian, Dutch fellen, Old High German fellen, German fällen, Old Norse fella, Danish fælde), causative of *fallanan (source of Old English feallan; see fall (v.)), showing i-mutation. Related: Felled; feller; felling.

"cruel," late 13c., possibly late Old English, perhaps from Old French fel "cruel, fierce, vicious," from Medieval Latin fello "villain" (see felon). Phrase at one fell swoop is from "Macbeth." Related: Fellness.

"rocky hill," c. 1300, from Old Norse fiall "mountain," from Proto-Germanic *felzam- "rock" (source also of Old High German felisa, German Fels "stone, rock"), from PIE root *pel(i)s- "rock, cliff." Old High German felisa "a rock" is the source of French falaise (formerly falize) "cliff." Now mostly in place-names, such as Scafell Pike, highest mountain in England.

past tense of fall (v.), Old English feoll.

"skin or hide of an animal," Old English fel "skin, hide, garment of skin," from Proto-Germanic *fella- (source also of Old Frisian fel, Old Saxon fel, Dutch vel, Old High German fel, German fell, Old Norse fiall, Gothic fill "skin, hide"), from PIE *pel-no-, suffixed form of root *pel- (3) "skin, hide." Related: Fellmonger.