The history of the usage of the word Internet is somewhat murky; the term was used in 1974 in the RFC 675 (Request for Comments) which was published by three individuals,
RFC 675 outlined a specification for the Internet Transmission Control Program; sometimes referred to as the Internet TCP. Those familiar with the history of the Internet will instantly recognise the name Vint Cerf; Vinton Gray Cerf is referred to as one of the "founding fathers" of the Internet: due to his work on the TCP/IP technology.
However, at that stage - the 1970s to 1980s - the term Internet was simple used as an adjective; aka, a word which was used to describe the inter-networking of transmission programs etc. Only by the 1990s was the term Internet used as a noun; aka, a word which denoted a thing: the network of computers which used the TCP/IP technology to communicate with one another.
The term Internet did have some competition in the 1990s; the term 'Information Superhighway' was another popular term used to describe the network of computers which used the TCP/IP technology. The term Information Superhighway was used by the US politician and presidential candidate Al Gore. Al Gore is credited with being responsible for providing crucial political support for the Internet during the 1990s as Vice-president of the United States. However, by the year 2000, the term Information Superhighway was out of vogue. The term 'the cloud' has tentatively been used to describe the Internet as of 2010-2012.