Further to other comments, looking here it seems that C, X, V for Copy, Cut, Paste were first used by Apple in the Lisa in 1983 and then later adopted by Microsoft for Windows:
"The IBM Common User Access (CUA) standard also uses combinations of the Insert, Del, Shift and Control keys. Early versions of Windows used the IBM standard. Microsoft later also adopted the Apple key combinations with the introduction of Windows, using the control key as modifier key. For users migrating to Windows from MS-DOS this was a big change as MS-DOS users used the "copy" and "move" commands."
"The IBM Common User Access (CUA) standard also uses combinations of the Insert, Del, Shift and Control keys. Early versions of Windows used the IBM standard. Microsoft later also adopted the Apple key combinations with the introduction of Windows, using the control key as modifier key. For users migrating to Windows from MS-DOS this was a big change as MS-DOS users used the "copy" and "move" commands."
https://en.wikipedia.org/wiki/Cut,_copy,_and_paste#Populariz...