A Matross was the term for a private in a train of artillery (a gunner's mate). One of the soldiers who assisted the gunners in loading, firing, and also sponging the guns to stop them overheating. "They carried flintlocks and marched with store wagons, acting as guards" 
In India in the earlier years, approximately to 1800, only the term matross was used, while in later years, only the term gunner is used, with an intermediate period when both terms were used.
Historical books online
- "Matross" pages 562-563 Hobson-Jobson: the Anglo-Indian Dictionary by Henry Yule, Arthur Coke Burnell, William Crooke "New Edition" 1903 Archive.org
- ↑ A Tug on the Thread by Diana Quick pub. 2009