1996: Mac OS - History of Desktop OSs
With the arrival of version 7.6, Apple dropped the "System" moniker from its Mac OS System operating system brand. The first version of Mac System Software was released in 1984, but it would take 12 years until the new brand is introduced. Mac OS was believed to be name that could be more effectively trademarked.
On the technology side, Mac Os 7.6 dropped support for Macs that were based on Motorola 68000 processors. Apple kept the Mac OS brand until version 8.6, after which it moved to Mac OS X.