I hear:

Ol' Kimball
Give me money
'N' ol' Muskie
He bet more.
Tell Kimball
Yo' musclin'
Through the keyhole
In the door.


"Musclin'" or not, the word is absolutely not "mother" or "murder." "Muzzlin'" is a possibility.

It's also possible that Smith was singing something he'd misheard originally, or that he forgot the words and plugged in nonsense: hence the alleged break in the recording while he took time to think of the right words and couldn't.