The ex

Delian said:
Well, it would be kinda strange to say muscle_expansion, tail_expansion, feet_expansion..

So to be consistent, we would actually need to alias them all to growth, because expansion sounds wrong in most cases.

Parts of the body involved in common sex appeal make sense as being expansion, though. Butts, breast, penis, balls, nipples, areola, pussy/vulva, and clitoris.