From Proto-Germanic *-as, *-is.
From Latin -ēs, the accusative plural ending of most third declension nouns.
From Middle English -es, from Old English -as, nominative-accusative plural ending of masculine a-stem (i.e. strong) declension nouns, from Proto-Germanic *-ōs, *‑ōz, from Proto-Indo-European *-es, *-oes (plural ending). Cognate with English -s (plural noun ending).