“… William Shakespeare knew how to invent a phrase with legs, as they say in show business. ‘At one fell swoop’is just one of thousands of words and phrases in everyday use that can be traced back to Shakespeare’s pen, including â€˜eyeball,â€™ â€˜madcap,â€™ â€˜softhearted,â€™ â€˜cold-blooded,â€™ â€˜downstairs,â€™ â€˜inaudibleâ€™ and â€˜radiance.â€™ Incidentally, if you’re interested in learning more about the surprising range of Shakespeare’s linguistic inventions, you should grab a copy of â€˜Coined by Shakespeareâ€™ (Jeffrey McQuain and Stanley Malless, Merriam-Webster, 1998), which explores more than 200 of old Will’s wonderful words.
“‘At one fell swoop,’ which was coined by Shakespeare in his play “Macbeth” in 1605, is a metaphor intended to conjure up the sudden, savage attack of a falcon or other bird of prey on its quarry.”
“… â€˜fellâ€™ in this case comes from an Old French word â€˜fel,â€™ meaning â€˜grim, merciless, or terrible.â€™ â€˜Fellâ€™ in this sense is obsolete in English, and just about the only place you’re likely to see it is in the combined form â€˜fell swoop.â€™ But the root word â€˜felâ€™ is very much with us in the words â€˜felonâ€™ (meaning originally â€˜a cruel man,â€™ then â€˜a villainâ€™) and related forms such as â€˜felonyâ€™ and â€˜felonious.â€™”
Felonious Swooping, some webpage I wandered into