The Free On-line Dictionary of Computing (30 December 2018):

Defense Advanced Research Projects Agency
Advanced Research Projects Agency
ARPA
DARPA
Defense Advanced Research Project Agency

    (DARPA, ARPA) An agency of the US Department of Defense
   responsible for the development of new technology for use by
   the military.  DARPA was established in 1958 in response to
   the Soviet launching of Sputnik, with the mission of keeping
   the US's military technology ahead of its enemies.  DARPA is
   independent from other more conventional military R&D and
   reports directly to senior DoD management.  DARPA has around
   240 personnel (about 140 technical) directly managing a $2
   billion budget.  These figures are "on average" since DARPA
   focusses on short (two to four-year) projects run by small,
   purpose-built teams.

   ARPA was its original name, then it was renamed DARPA (for
   Defense) in 1972, then back to ARPA [When?], and then,
   incredibly, back to DARPA again on 1996-03-11!

   ARPA was responsible for funding development of ARPANET
   (which grew into the Internet), as well as the Berkeley
   version of Unix and TCP/IP.

   (http://darpa.mil/).

   History (/pub/misc/darpa).

   (1999-07-17)