Definition of "foretopman"

It was a warm night for the latitude; and the Foretopman, whose watch at the time was properly below, was dozing on the uppermost deck whither he had ascended from his hot hammock

1924, Herman Melville, chapter 12, in Billy Budd‎, London: Constable & Co.

WHEN Jimmy Fallon showed up on NBC ’s “Late Night” last week without a sidekick, it looked like yet another sign that the Ed McMahon era is over; so many talk show hosts work solo that the second-banana position seems almost as obsolete as the foretopman or the Linotype operator.

2009 March 8, Alessandra Stanley, “The Vanishing Sidekick”, in New York Times‎