The forecastle is the upper deck of a sailing ship forward of the foremast, or, historically, the forward part of a ship with the sailors' living quarters. Related to the latter meaning is the phrase "before the mast" which denotes anything related to ordinary sailors, as opposed to a ship's officers.

What is a forecastle on a ship?

The fo'c's'le or forecastle is the forward deck of the ship. It derives its name from sailing ship days when the raised forward deck was known as the forecastle. This was typically a raised, castle like structure where archers first could engage enemy ships. The anchoring gear or ground tackle may be seen here.

Where does the word forecastle come from?

forecastle (n.)

as Anglo-French forechasteil), "short raised deck in the fore part of the ship used in warfare," from Middle English fore- "before" + Anglo-French castel "fortified tower" (see castle (n.)).