Means too tired to participate, too worn out.
Originally meant too old to play with the cool kids, from the Chuck Berry song. Lyrics below:
"
Casey finally learned to do the hoochie koo
This might have been fine back in '
22
Now, I is gonna give you fellows just a little tip
If you wanna keep your girl youse better get hip
"Or, you'll be too pooped to pop, too old a soul
You hips are gettin' weaker when you try to do the stroll
And every time your
feet gettin'?to go in one way
Here comes a new
dance you'll be left to stray.