The right side of a ship or boat when you're facing toward the front, used as a directional term by sailors.
From Old English 'steorbord' combining 'steor' (steering) and 'bord' (board or side). The steer-board was the right side where the steering oar was originally placed on ships.
Starboard seems random until you learn it literally means 'steering board'—that's where Vikings and ancient sailors put their steering oars, and the name stuck even after ship design changed completely.
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