Where does the phrase "Cat's Pajamas" come from?

Factual Questions
1

A friend of mine started using it…and while I know it means good. I have no idea what it orginates from.
-Damien

2

I’ve often heard the phrase “cat’s ass” in the same context. Maybe PJ’s is the more genteel version. How they arrived at PJ’s… or even ass for that matter… is beyond me.

3

Sound’s like Dr. Seuss to me. Don’t know.
I’ve heard it too.
Peace.
mangeorge

4

It was just a nonsense phrase popular in the 1920s. Others included the Bee’s Knees, the Eel’s Eyelashes, the Tadpole’s Tonsils, etc. There was a late-20s novelty song called “Sheba, Please Be Mine!” which used a whole lotta them.

5

And there I was thinking people may have once been making pajamas outta cats.

-Damien