Or as my toddler calls it, poop *giggle*! This is used especially of fungi, but I assume it also applies to, say, the larvae of dung beetles, which live inside the ball of the stuff that their parents roll up and then lay eggs inside. Coined in 1874 from Latin roots fimus, dung + colere, to inhabit. First citation in the OED, from a treatise on fungus:
Only seven or eight ... do not occur on dung, whilst fifty-six are fimicolous.