Overview
Apple's iOS did not have an official name until the release of the iPhone software development kit (iPhone SDK) on March 6, 2008. Before then, Apple marketing literature simply stated that their iPhone runs a version of "OS X", a reference to iOS' parent, Mac OS X. When introduced, it was named iPhone OS. It was renamed iOS on June 7, 2010, as iPhone was no longer the only device to run iOS. Apple licensed the "iOS" trademark from Cisco.
Read more about this topic: IOS Version History