one fell swoop, one full swoop, one fowl swoop...

Factual Questions
1

Which is correct? Any insight on its origins?

2

http://www.word-detective.com/back-c.html#fellswoop

3

One Swell Foop

4

The phrase comes from Shakespeare’s Macbeth – Macduff has just been told that while he’s been out of the country Macbeth has had his entire family killed:

He has no children. All my pretty ones?
Did you say all? O hell-kite! All?
What, all my pretty chickens and their dam
At one fell swoop?

5

One fell swoop.
From Macbeth, as Katisha noted.
“Fell” in the sense of cruel and destructive.
“Swoop” in the sense of a bird of prey descending on its prey with closed wings – i.e. swiftly.

6

Here is a very old thread on the subject.