[1] The headword, accusative plural, is evidently quoted from somewhere. Same gloss in Photius (omicron458 Theodoridis); cf. Harpokration (on o)rika/), a scholion on Plato, Lysis 208A, and Hesychius omicron1170. According to Chantraine, o)reu/s (epic/Ionic ou)reu/s) etymologically means the animal that makes a furrow (o(/ros), mules being preferred to oxen for plowing. A folk etymology connects the word with o)/ros "mountain"; this may account for the smooth breathing of the Attic o)reu/s.
[2] Similar notes in ps.-Herodian and Pollux. See also omicron 532.