The headword is the present active infinitive of the compound verb e)piyau/w. If it is quoted from somewhere (rather than being merely paradigmatic), extant possibilities begin with Pindar and Sophocles.
cf. epsilon 2783, psi 30.
[1] Comparably, according to Adler, in the Syntacticum Laurentianum and Syntacticum Gudianum. In fact, this verb is more usually construed with a genitive: see LSJ s.v.
[2] Same glossing synonym in Synagoge epsilon780 (and Photius, Lexicon epsilon1812).