[very common] A mythical figure like the Unknown Soldier; the archetypal hacker nerd. This term is one of the oldest in the jargon, apparently going back to MIT in the 1960s. See random, Suzie COBOL. This may originally have been inspired by ‘J. Fred Muggs’, a show-biz chimpanzee whose name was a household word back in the early days of TMRC, and was probably influenced by ‘J. Presper Eckert’ (one of the co-inventors of the electronic computer). See also Fred Foobar.