Gruniożerca translates to Grunio the Devourer. Grunio is the name of this actual guinea pig.
@arhneu The "gru" prefix is a Slavic onomatopoeia for the purring/cooing noise a guinea pig makes. The suffix is there to make it into a pronounceable name. Roughly translated: "The one that purrs".
Żerca means eater or devourer. https://en.wiktionary.org/wiki/%C5%BCerca
So, it seems Gruniożerca could be more literally translated as Purry the Devourer!