This distinction between the headword - not in LSJ - and the very similar ἤια (trisyllabic, besides the initial eta) summarizes the more explicit one in Hesychius s.v., which glosses ἐία as "either fodder or its provision". Together with Suda s.v. eta 140 (ἤιον is "food for a journey"), the essence of the distinction seems to emerge as that between animals and humans.