Quenya 

-on

name

-on gen.pl. ending (3O), in aldaron, aranion, elenion, Eldaron, #esseron, Ingweron, Istarion, Númevalion, Quendion, Silmarillion, Sindaron, tasarion (see Nan-Tasarion), Valion, wenderon, yénion. Normally the ending -on is added to the nominative plural, whether it ends in -i or -r, but some nouns in -ë that would have nominative plurals in -i seem to prefer the ending -ron in the genitive (hence #esseron as the gen. pl. of essë "name", though the nominative pl. is attested as essi and we might have expected the gen. pl. *ession; similarly wenderon, Ingweron).