I am of Arabic background and I have never heard of anyone who was just plain Abdul. It's always something more complete, like Abdul Aziz or Abdul Rahman. And naming someone something meaning simply "servant of the" wouldn't make sense. People should realise that Abdul is not a full name.
Abdul is not used as a full name in the Muslim world, only as part of a name. It's more likely an English name (particularly used by African-Americans) based on an Arabic name.