The lemma θαλαττοκοπεῖς comes from Aristophanes, Knights 830 (see web address 1). For the verb, see also Libanius Declamationes 26.1.18 and Suda mu 768 and pi 1712.
[1] This first definition is found in Photius and Hesychius under the same lemma, θαλαττοκοπεῖς .
[2] From ταράττῃ through κύματα appears to derive from the scholia to Aristophanes, Sch. in Eq. 830a "τί ταράττῃ καὶ θορυβῃ̂; ἔλαβε δὲ τὴν χρῆσιν τοῦ ὀνόματος ἀπὸ τῆς θαλάττης. ἐπειδὰν γὰρ ὑπὸ σφοδροτέρων ἀνέμων ταραχθῃ̂ τὰ κύματα, ἀλλήλοιh συγκρούουσιν. "
[3] For this reference to dream interpretation by the patriach Nicephorus, compare beta 351, kappa 1663, mu 302, pi 1841, sigma 133, sigma 1129, tau 1036, omicroniota 134, and upsilon 49. All these dream interpretations come from a collection of 101 iambic verses which are usually attributed to Astrampsychus (alpha 4251). The name Astrampsychus may well be an alias or a misguided assimilation to the similarly dubiously named author of the Sortes Astrampsychi or Oracles of Astrampsychus (4th cent. AD), which enjoyed popularity with both pagan and Christian audiences--see Bryn Mawr Classical Review 2001.10.04 (web address 2).
Four verses of iambic trimeter--with faulty scansion of ἰδεῖν --from the dream interpretations attributed to this Astrampsychus start with θάλατταν . For a Greek text and Latin translation of the 101 verses of Astrampsychus, see C. B. Hase 1823, pp. 395-412 (web address 3).