Google first announced Android O in March and then released a beta on supported devices last month. There has been much debate about what it would be called in its final form, with many taking guesses with inspiration from their favorite sweet snacks. While many hope that it will arrive as Android Oreo, it appears that some eagle-eyed folks might have stumbled upon its internal name where it goes by 'Oatmeal Cookie'.
The moniker was discovered when folks were looking through the code of the OS and discovered many references to 'oc'. Although examples like ‘oc-dev’ and ‘OC-MR1’ mean nothing on their own, slides with code shown during Google I/O 2017 included references to 'oatmeal_cookie' which could be what the abbreviation stands for.
Internal designations for Android have been used in reference to past versions of the mobile operating systems, with the more recent ones being Android K as 'Key Lime Pie' and Android L as 'Lemon Meringue Pie'. While Oatmeal Cookie might be its internal name, this will most likely not be the final name that will be presented to consumers.