One Fell Swoop

Does anyone know the orign of " one fell swoop"? I've searched but can't find the answer.

The phrase stems from a passage in Macbeth. Macduff has just been told that his wife and children have been killed:

All my pretty ones?
Did you say all? O hell-kite! All?

What, all my pretty chickens and their dam

At one fell swoop?

(Macbeth IV.iii.216ff)

Macduff is speaking metaphorically, with Macbeth as the bird of prey ("hell-kite") and his wife and children as chickens. Fell means 'fierce; cruel; savage; deadly', and swoop is just 'an act of swooping, as by a bird of prey' (and this passage is the first use of swoop in that sense in English), so the line literally means 'in one fierce pounce'.

The line began to be used figuratively to mean 'by as if by one blow; all at once; all together', which is now the only meaning; the literal sense has been largely forgotten.

The word fell in this sense, now rare or archaic, comes from the same Old French word that gives us the English word felon. Swoop is a variant of the Old English word that gives us the modern word sweep.

I remember Henley's "...in the fell clutch of circumstance..." Is that the same use of "fell?" I can't recall any other use of the word.