The headword tanah/ is nominative singular feminine of the epic/tragic adjective tanao/s. (In the quotation which follows, the adjective takes the Doric form tanaa/.) Similarly glossed in Hesychius and a scholion on Homer, Iliad 16.589 (where the adjective appears in the genitive). The lexica's nominative is probably generated by that passage, but note also Oppian, Halieutica 1.213, where the nominative occurs and the scholia gloss with this adjective amongst others.
[1] Greek Anthology 6.52.1-2, attributed to Simonides; cf. eta 597, mu 504. (But read poti\ "against" instead of the Suda's a)nti\.) See another extract from this epigram, the dedication of a spear, at tau 418.