This might have been a case of parallel invention. When I was using Michigan Terminal System in 1981, and it wasn't new then, I remember SERCOM/MSINK being dist

This might have been a case of parallel invention. When I was using Michigan Terminal System in 1981, and it wasn't new then, I remember SERCOM/MSINK being distinct from SCARDS/SOURCE and SPRINT/SINK. Yes, that's cards as in punch cards. My impression is that similar concepts and terminology have also existed in the IBM world since $forever. I doubt that the MTS folks and the Bell Labs folks were aware of each others' identical inventions, but if there was a relationship I'd bet on the MTS folks having been first.