I would very much doubt it is a name. I think the M may relate to the 3rd Battalion The Leinster Regiment being Militia. Regiment ceased to exist in 1922. You will find information on both regiments with a google/wiki search. Regards, Paul.
https://en.wikipedia.org/wiki/Prince...oyal_Canadians) I'll let you search for the Scottish Rifles which is the title 2nd Cameronians used.