The headword eu)mare/h is otherwise attested only in the derivative entry in ps.-Zonaras (908.223) and in the Glossae in Herodotum on Herodotus 2.35.3 (n. 2 below) -- a passage where in fact many manuscripts have the dative singular eu)mare/h| rather than the eu)marei/h| preferred by modern editors. It appears to be a Byzantine form of eu)ma/reia (cf. Hesychius s.v. [epsilon6976], with similar glossing) or eu)marei/a, the latter with long final alpha. See epsilon 3574, epsilon 3575.
[1] cf. alpha 3468, alpha 3469, and see generally LSJ s.v.
[2] Herodotus 2.35.3 (web address 1), and also Herodotus 4.113.1 (web address 2); for the latter see again epsilon 3575.