LSJ
ἡ, epith. of Thetis, Il. 20.207; νέποδες καλῆς ἁλοσύδνης, of seals, Od. 4.404 (expl. by Gramm. as ΄child of the sea΄); of Nereids, A.R. 4.1599; cf. ὑδατοσύδνη. (Perh. containing the root of ὕδωρ.)
Liddell-Scott-Jones, Greek-English Lexicon (9th ed., 1940)