Online etymology

eponym:
"one whose name becomes that of a place, a people, an era, an institution, etc., 1846, from Gk. eponymos "given as a name, giving one's name to something," from epi “upon” (see epi-) + onyma, Aeolic dial. variant of onoma "name" (see name)."

When you look at the meaning of the word "eponym" : litt.
"upon" and "name"
the word does not make a specific difference between the name of a person and the name of a thing; so a thing named after a thing simply stays an eponym (to me).

centaur + centaur = eponym + eponym