"OS X has been with us for over 15 years," said Craig Federighi, the Apple executive who leads Mac and iOS development, during Monday's Worldwide Developers Conference (WWDC) keynote. "But we thought there would be a name so much cleaner and so much more elegant."
The rebranding will put the Mac's operating system more in sync with the nomenclature of Apple's other OSes, including iOS, tvOS and watchOS.
But macOS wasn't out of the blue: Apple used a variation -- Mac OS -- between 1995 and 1997, when it licensed third-party OEMs (original equipment manufacturers) to build and sell Mac clones. (Co-founder Steve Jobs ended that strategy shortly after he returned to Apple in 1997.) Apple retained U.S. trademark rights to Mac OS; those rights were last renewed in 2015.
Prior to Mac OS -- starting in 1984 with the Mac's debut -- Apple simply dubbed the operating system as System, befitting the graphical user interface's (UI) minimalism.
The now-defunct OS X moniker originated in 2000, when it was officially designated Mac OS X. Apple ditched the "Mac" adjective in 2012. The last version of OS X, the still-current-for-now El Capitan, was the 11th in a line that started with Cheetah and ran through nine iterations named for big cats before switching to California locales with 2013's Mavericks.
In keeping with the in-state them, Federighi today tapped this year's name plate as "Sierra" to evoke the California mountain chain.
macOS Sierra will release this fall, Apple said today, and will be available to the general public for preview testing in July. Users interested in grabbing the previews can register with Apple's beta program on the company's website.
Registered developers receive the Sierra beta today.