Ancient Greek 
Attested by Herodotus (2.32). Perhaps from συρτός "swept, washed down", from the verb σύρω trahere, "draw, drag, trail along", after the effect of the wind and the waves on the quicksands in these gulfs.
The metaphorical meaning "destruction" is due to the proverbial difficulty of navigating these gulfs due to shoreward drag.
Proper noun 
Σύρτις, σύρτις f
- the Syrtis, name of two large shallow gulfs on the coast of Libya
- Συνεχὴς δ’ἐστὶν ἡ μικρὰ σύρτις, ἣν καὶ Λωτοφαγῖτιν σύρτιν λέγουσιν. (Strabo, Geographica, 17.3)
- destruction, ruin
- ἄλλα δ’ ἄλλαν θραῦεν σύρτις (Timotheus Fragmenta, ed. D.L. Page, Poetae melici Graeci, Oxford: Clarendon Press, 1962, 1967, 400‑418; fragment 15, line 88)
- Henry George Liddell, Robert Scott, A Greek-English Lexicon.
- John Lemprière, A classical dictionary: containing a copious account of all the proper names mentioned in ancient authors; with the value of coins, weights and measures, used among the Greeks and Romans; and a chronological table (1827), p. 790.