https://www.cnet.com/news/mojave-is-the-new-mac-os/

This ends "a four-year mountain bender," said Craig Federighi, Apple's senior vice president of software engineering, at the Worldwide Developers Conference on Monday in San Jose, California.

After years of giving cat-related names to its Mac software (Leopard, Lion, Mountain Lion), Apple in 2013 shifted to California-themed titles for future versions of the OS with OS X 10.9, aka Mavericks. Two years ago, the company dropped the "X" from its computer software, instead making it the cleaner "MacOS." The particular flavor that launched in 2016 was dubbed Sierra, and its successor last year was called MacOS High Sierra.