Liksewise in other lexica (references at Photius omicron77 Theodoridis) and in the scholia to Homer, Iliad 5.137, from where the headword is quoted. It is an epic dative plural of the old i-stem noun o)/i+s (cf. omicron 95, omicron 98, omicron 100). The dative plural ending -essi seems to have been extracted from s-stem nouns like genos; it occurs also in Aeolic dialect inscriptions. See Smyth §250 D (web address 1).