from The Century Dictionary and Cyclopedia
- n. One of a number of the crew who are stationed on the forecastle of a man-of-war.
Sorry, no etymologies found.
A forecastleman, addressing a petty officer, inquired how she could hail from San Francisco, then belonging to the United States, and fly the Peruvian flag.
"Hallo, what's the matter?" here came growling from a forecastleman awakened from his deck-doze by Billy's raised voice.