From Old English 'maest,' from Proto-Germanic *mastaz — the vertical element of a sailing ship supporting the sails.
A tall vertical pole or spar rising from the keel or deck of a sailing vessel, used to support the sails, rigging, and yards.
From Old English 'mæst' (a mast, a pole), from Proto-Germanic *mastaz (a mast, a pole), possibly from PIE *mazdo- (a pole, a rod) or from *mad- (moist, wet — with a connection through the idea of a 'wet' or sap-filled tree used for a mast). The word is common to all Germanic languages and predates written records. The mast was the single most important structural element of a sailing vessel — the vertical pole that converted
The phrase 'before the mast' meant to serve as a common sailor — because ordinary crew slept in the forecastle, the area of the ship forward of the foremast, while officers had cabins aft. Richard Henry Dana's 'Two Years Before the Mast' (1840) made the phrase famous as a description of the harsh life of working seamen.