Which one came earlier, the TCP/IP reference model or OSI model?
The TCP/IP model, which is realistically the Internet Model, came into existence about 10 years before the OSI model. The four-layer Internet model defines the Internet protocol suite, better known as the TCP/IP suite. TCP and IP are actually two of the many protocols that make up the Internet protocol suite such as FTP, UDP, SNMP, SMTP, Telnet, etc.
The OSI model (Open Standards Institute) is an internationally accepted generic model for all new protocols to be designed around and older protocols -- such as TCP/IP -- to fit into. This was created so that an open platform can be used to allow multiple protocols to communicate with each other as long as they followed this model.