- The section from amidships to the stern of a vessel on either side (i.e. port/starboard quarter).
- Referring to a bearing of 45 degrees on either side from dead astern.
16th century. Apparently in reference to the quarterdeck.
Essentially, the opposite of the direction of the port/starboard bow. Hence, if a vessel is divided up into fourths, the quarters would be the two adjacent corners opposite the bow. It can also refer to the direction that the wind is striking the vessel, such “on the port/starboard quarter,” meaning that the wind is coming from astern on some bearing.
Rogers, J.G. (1985). Origins of Sea Terms. Mystic Seaport Museum.