Hello Jumborex! Benvenuto! As English is not my first language (Spanish is) I had the same problem that you and I needed to search for it. Apparently, a windlass is basically some big pulley used in ships but as the others explained, it use is metaphorical. A ship is a windlass when she only takes cargo from above to below and back, a very mechanical and repetitive work. So offensive for the Captain of the ship.
By the way, the word windlass was so perfect, it sounded like a super heroine, like "aqua boy and wind lass"
. I was disappointed when I discovered that was not the case. For instence, "The aeronaut and the windlass" would have been a beautiful title for a love story between a globe aviator and a mystical spirit like Ariel in the Tempest
(Sorry, that is the sort of things I think when I am alone at work)