Big Fat Hen?

A remake of Nightmare on Elm Street is coming out, and I remember how I got freaked out when the little kids would sing . . .

One, two, Freddy's coming for you
Three, four, better lock your door
Five, six, grab your crucifix
Seven, eight, gonna stay up late
Nine, ten, never sleep again.

This, of course, is based on the famous nursery rhyme:

One, two, buckle my shoe
Three, four, knock at the door
Five, six, pick up sticks
Seven, eight, lay them straight
Nine, ten, a big fat hen

I looked up this song, found that it dates back to the early 1800's, but there is no known explanation of the lyrics. It seems to me that it's a series of requests for someone to do stuff, and then they throw in that last line about the hen out of nowhere. Let's pretend for a moment Dr. Ken was there in the 1800's . . .

English Bloke: One two buckle my shoe.
Ken: Sure. I guess.
EB: Three, four, knock at the door
Ken: Okay, I'm on it, but you don't have to count like that. I'll hook you up.
EB: Five, six, pick up sticks
Ken: Wait, I haven't even got to the door yet. Do you want me to get the sticks before I knock or after? Am I giving this person sticks or can that wait?
EB: Nine, ten, a big fat hen
Ken: Do you want me to find a big fat hen and give it to whoever is in that house, or are you calling me a big fat hen? Either way, you got some big British balls saying some shit like that after I've done all this random crap for you. If I do find a hen at this hour, I'll gladly give it to the guy in the house, but not before I stuff it up your ass like a turducken!