There is no standard. Some people create a standard of their own while some use naming conventions and others just use them willy-nilly.
If you need it to be obvious for its use (like in a team environment) then you could go with a naming convention, something long and painful to read like:
Example of naming for per channel masks:
MyAwesomeDudeMask_rAO_gRough_bMetal
Example of naming for per model area masks:
MyAwesomeCarMask_rMetal_gPlastic_bGlass
Really do whatever you like. As for how that specific texture was used you just have to either look at the material it is used in or suss it yourself by applying each channel and seeing how it fits. Remember, some masks are for channels while others may be for assigning to locations on a mesh.