What is the meaning of -eren?

forms the plural of a limited group of nouns: blad, been, ei, gelid, gemoed, goed, hoen, kalf, kind, kleed, lam, lied, rad, rund, volk

part of the infinitive of verbs borrowed mainly from French and Latin, e.g. informeren from French informer (to inform).

frequentative verbal suffix; indicating repetition

Source: wiktionary.org