What's UNIX (jokes) Short answer: Unix stands for UNiplexed Information and Computing System.
(It was originally spelled "Unics.")

Long answer: Coined in 1969 to describe a specific computer operating system,
the term "Unix" now covers a whole host of variations, including Linux, FreeBSD,
and Solaris. The name was intended as a pun on an earlier system called "Multics"
(Multiplexed Information and Computing Service).

That side splitting pun is the key to understanding the acronym,
since the word "uniplexed" doesn't seem to mean anything in particular.
("Multiplexed" refers to a communications system able to carry many messages simultaneously.)