macOS and OS X version code-names

From 2001 to 2012, OS X was code-named internally (for development purposes) after big cats. Becuase Apple marketing was also using those code-names to promote OS X publicly, however, the company's development crew switched their internal naming structure to wines beginning with OS X 10.3 — publicly known as Panther, privately as "Pinot." (Apple did make one exception for OS X 10.6, which never had a code-name beyond Snow Leopard.)

Though Apple's external code-names for OS X switched to California places in 2013, the internal code-names remained wine-based until 2014. In 2015, the development team switched to types of apples, with OS X 10.11 El Capitan (AKA "Gala").

In 2016, OS X officially became macOS, though Apple continued using California places as the external code names, and apple types as the internal code names. So far, this has remained the internal code name across the board.