What Does Advanced Research Projects Agency Mean?
The Advanced Research Projects Agency (ARPA) was the old name for the Defense Advanced Research Projects Agency (DARPA), an agency of the U.S. government responsible for developing new technology for the military.
In computing, ARPA/DARPA is best known for its involvement in networking and the early development of ARPANET, a network that many view as the starting point of the Internet.
Techopedia Explains Advanced Research Projects Agency
ARPA changed its name to DARPA in 1972, then back to ARPA in 1993, then finally back again to DARPA in 1996. Its name change also sometimes causes confusion in the naming of ARPANET, who some assume changed its name to DARPANET, which is not the case.