TMZ which is a celebrity gossip and news website and TV show and was founded by Harvey Levin in the year 2005 but is now owned by Warner Media since the year 2009 stands for "Thirty Mile Zone".
The thirty mile zone is the historic "studio zone" within a 30-mile radius that is centered at the intersection of West Beverly Boulevard and North La Cienega Boulevard in Los Angeles, California.
So the TMZ is just short for Thirty Mile Zone and I used to think it stood for something else until I looked it up online.