Bob Coltman: yes, wampus sounds like a corruption of rumpus to me. Substituting w for r is common when children are learning to speak, so again there's a possibility that this version came out of the nursery even if the word didn't begin there.

I had a brilliant but bonkers Birman cat called Womtious, a name chosen because the white parts of her paws didn't match as they should on a show quality animal. We found the word in 'A Dictionary of the Sussex Dialect', published in 1875 by a vicar and augmented in 1957 by a dotty upper-class lady. I've found the relevant page online: Caterwise comes from the 1875 edition and Caterwomtious must have been added in the 1957 version.

Valmai