The reason why - I cannot tell;
But this I know, and know full well,
I do not like thee, Dr Fell.
It's only just occurred to me, but perhaps one of the reasons Tom Brown disliked the poor man (John Fell, 1625–1686, was the dean of Christ Church college, Oxford) was because he went by the name of Fell.
I'm afraid it's a word of ill-omen.*
All right, fell seams in needlework aren't particularly sinister, except that they're associated with sides-to-middling. (This is an ancient and very dull craft previously employed by poor people. You cut a worn bed sheet down the middle lengthways, turn the less-worn sides to the middle and sew them together. It means you're always sleeping on a seam. A fell seam.)
Definitely sinister is the fell of one fell swoop, where fell means cruel or terrible or even deadly.
Then there's the fell of fell-walking. Now, the fells of Northern Britain are glorious and beautiful in good weather:
Fair Snape Fell.
but unfortunately it hardly ever is.
Lastly, we have the fell which means an animal skin or hide. And, I mean, eu!
Now, I'm sure there are thousands of lovely fluffy bright and beautiful people all over the world called Fell.
If you see one, do make a point of loving them as much as is humanly possible.
It can't be easy, you know.
Word To Use Today: fell. The falling-down and needlework meaning comes from the Old English fellan; the cruel meaning comes from the Old French fel, from the Mediaeval Latin fellō, which means villain; the animal hide comes from the Old Norse berfjall, bearskin, and before that from the Latin pellis, skin; and the tract of upland moor comes from the Old Norse fjall, related to the Old High German felis, rock.
*Especially if you're a tree.