The primary headword, usually spelled with an omega (e)perrw/santo) is a word from hexameter poetry, most famously Homer, Iliad 1.529 (web address 1, and see at alpha 1538), in reference to the hair of Zeus as he nods in assent. A large percentage of the attestations result from quotations of or commentary on this passage.
[1] So far, the entry = Apollonios Sophistes, Homeric Lexicon 71.17, Lexica Segueriana 227.24, and Photius pi1433 Theodoridis; this gloss also appears in the course of longer entries at Hesychius epsilon4442 and (post-Suda) Etymologicum Magnum 335.31.
[2] Third person plural, aorist, of e)pirroqe/w (very probably quoted from Euripides, who has three instances; cf. Hesychius epsilon5130). Perhaps the Suda or its source mistakenly believed this to be a form of the same verb as the headword. The Suda's idiosyncratic spelling of the headword with omicron may have given rise to that notion. Adler cites the unedited lexicon of Codex Laurentianus 59.16 as a comparandum.