Late 16th century: variant spelling of boatswain.

• cox from mid 19th century:

  The cox or coxswain (Middle English) is the person who steers a racing boat or similar craft. The cox part is from the old word cock (Late Middle English) ‘small boat’, which is not related to the bird but to Latin caudex or codex ‘block of wood’. The second half of the word, swain (Old English), now means ‘a country youth or peasant’ but was originally ‘a young man attending a knight’ and ‘a male servant or attendant’. It is also the second half of boatswain (Late Middle English) (often abbreviated to bo'sun), a ship's officer in charge of equipment and the crew.