Note 6 — BOOK VI. AN ACCOUNT OF COUNTRIES, NATIONS, SEAS, TOWNS, HAVENS, MOUNTAINS, RIVERS, DISTANCES, AND PEOPLES WHO NOW EXIST, OR FORMERLY EXISTED.
John Bostock translation
From βοῦς, an ox, and πορός, “a passage.” According to the legend, it was at the Thracian Bosporus that the cow Io made her passage from one continent to the other, and hence the name, in all probability, celebrated alike in the fables and the history of antiquity. The Cimmerian Bosporus not improbably borrowed its name from the Thracian. See Æsch. Prom. Vinc. l. 733.