The headword is a feminine noun in the accusative plural. See LSJ s.v. o)/xqh, and cf. omicron 1047, and eta 141 (gloss). It is extracted from Homer, Iliad 15.356 (web address 1), where Apollo knocks down the banks of a trench (see next note) that the Achaeans dug for their defensive perimeter.
[1] The headword is identically glossed in the Synagoge, Lexica Segueriana 323.21, and Photius' Lexicon (omicron739 Theodoridis); cf. Apollonius' Homeric Lexicon 125.23; Orion [Author, Myth], Etymologicum 123.34; Etymologicum Magnum 645.17 (Kallierges); and Hesychius omicron2025 s.v. o)/xqa. Adler also cites Etymologicum Genuinum. The gloss follows a scholion (= D scholia) to Homer, Iliad 15.356 (web address 1), in which the scholiast notes that the headword properly applies to a river.