The headword, which must be quoted from somewhere, is feminine accusative singular of o)nhto/s, from the verb o)ni/nhmi. Similar entry in other lexica: see the references at Photius omicron339 Theodoridis, where however the headword (out of alphabetical order) is transmitted as w)nhth/n -- quoted, Naber believed, from Thucydides 3.40.1 -- and the two glossing words (a)gorasth/n, e)napo/lauston) relate to w)nhth/n and o)nhth/n respectively.
The adjective o)nhto/s is attested only in lexicography; but Nick Nicholas points out that the genitive plural o)na/twn occurs in a possible fragment of Sappho (fr. 1a in Edmonds' 1922 Loeb edition of Lyra Graeca). An Attic red figure vase of c.430 depicts Sappho holding her own book, apparently entitled Winged Words, with the verse a)eri/wn e)pe/wn a)/rxomai a)ll' o)na/twn "I begin words that are airy but beneficial." Editors since Edmonds have not accepted this as a fragment of Sappho.