I have written here a couple of times about the 40+ year history of the UNIX® operating system, and its many “descendants”, including Linux and Mac OS X. UNIX began as a sort of “under the corporate radar” project at AT&T Bell Labs, following AT&T withdrawal from the MULTICS project. This month’s issue of the IEEE Spectrum has a feature article on the history of UNIX, which began as a simple system running on an orphaned PDP-7 minicomputer, made by Digital Equipment Corporation. The name of the system was a takeoff on the MULTICS name:
The name Unix stems from a joke one of [Ken] Thompson’s colleagues made: Because the new operating system supported only one user (Thompson), he saw it as an emasculated version of Multics and dubbed it “Un-multiplexed Information and Computing Service,” or Unics. The name later morphed into Unix.
The article gives a good overview of the many twists and turns, technical, legal, and otherwise, of the history of UNIX, and its derivatives. It’s worth a read if the history of technology interests you.