The headword is a (commonplace) masculine noun in the nominative singular (cf. alpha 3215 for it as a nickname). In the quotation given it appears in the accusative singular.
For cognates cf. mu 1307, mu 1308, mu 1309, mu 1310.
[1] George of Pisidia, Heraclias 3 fr.16. The Euphrates River is the longest river in western Asia and generally follows a course to the west of the Tigris River (cf. tau 559), with which in antiquity it was connected by various navigation and irrigation canals; cf. epsilon 1310, and see OCD(4) s.v.