LSJ
Arc. and Cypr. for ὅδε, declined like ὁ with addition of -νυ, nom. sg. masc. ὅνυ Inscr.Cypr. 141 H., acc. τόνυ ib. 140H., dat. τῷνυ Schwyzer 664.11 (Orchom. Arc., iv BC), acc. pl. neut. τάνυ IG 5(2).3.14 (Tegea, iv BC), gen. τῶννυ SIG 306.59 (ibid., iv BC), IG 5(2).262.23 (Mantinea, v BC), dat. pl. fem. ταῖννυ SIG 306.30 ; also, with -νυν for -νυ, acc. sg. fem. τάννυν, acc. pl. masc. τόσνυν, ib. 559.48, 49 (Megalopolis, found at Magn. Mae., iii BC).
Liddell-Scott-Jones, Greek-English Lexicon (9th ed., 1940)