Short for because it's time network, BITNET was a U.S. network of IBM mainframe systems founded in 1981. It was first established between the University of New York and the Yale University. In 1986, BITNET II was created to help bandwidth needs, which later merged with CSNET to form CREN in 1988.
As the Internet became popular in the 1990s, BITNET's usage declined and later became defunct and is no longer in use today.
When it was created, BITNET was short for because it's there network.