When we refer to OSI, we're actually referring to OSI/RM (Reference Model). In the early days of computing, like 20 yrs ago, the world was dominated by proprietary giants like IBM, DEC, Wang, Unisys, etc. ISO/OSI protocol was developed to try and sort of, OPEN up the proprietary nature of computing. Hence OPEN SYSTEM. However, the ISO/OSI protocol was never approved by the UN. TCP/IP became popular instead. As such, in schools, we learn the ISO/RM as a concept. Hope this helps.