Why-a-no-chicken?
Why- a- web (site)
via knot?

A pointless diversion into a Marx Brother's routine - this one from Cocoanuts.
Hammer [Groucho Marx]: ... Now here is a little peninsula, and here is a viaduct leading over to the mainland.

Chico: Why a duck? Hammer: I'm all right. How are you? I say here is a little peninsula, and here's a viaduct leading over to the mainland.

Chico: All right. Why a duck?

Hammer: I'm not playing Ask-Me-Another. I say, that's a viaduct.

Chico: All right. Why a duck? Why a--- why a duck? Why-a-no-chicken?

Hammer: I don't know why-a-no-chicken. I'm a stranger here myself. All I know is that it's a viaduct. You try to cross over there a chicken, and you'll find out why a duck. It's deep water, that's viaduct.

Chico: That's-why-a-duck?

Hammer: Look ... Suppose you were out horseback riding and you came to that stream and wanted to ford over there, you couldn't make it. Too deep.

Chico: But what do you want with a Ford when you gotta horse?

Hammer: Well, I'm sorry the matter even came up. All I know is that it's a viaduct.

Chico: Now look ... all righta ... I catcha on to why-a-horse, why-a-chicken, why-a-this, why-a-that. I no catch on to why-a-duck.

Hammer: I was only fooling. I was only fooling. They're going to build a tunnel in the morning. Now, is that clear to you?

Chico: Yes. Everything---excepta why a duck.