Если верить
Википедии, название состоит из операций, которые используются алгоритомом: умножение, циклический сдвиг (MUltiplication, Rotate).
The name comes from two basic operations, multiply (MU) and rotate (R), used in its inner loop.
The name, if you're wondering, comes from the simplest sequence of operations which will thoroughly mix the bits of a value - "x *= m; x = rotate_left(x,r);" - multiply and rotate. Repeat that about 15 times using 'good' values of m and r, and x will end up pseudo-randomized. Unfortunately multiply+rotate has a few major weaknesses when used in a hash function, so I used multiply+shift+xor. I liked the name Murmur better than Musxmusx, so I kept it.
Увы, с котиками это никак не связано.