Obvious Jew
An OJ is a Jew so obvious, even your grandma would know. They have names so Jewish, it's like they were born in a synagogue. Don't go around accusing every Daniel or Leah of being Jewish unless you're 100% sure.
'Daniel? That’s an OJ. No question.'
'Leah? She’s got the name of a real OJ.'
'He’s got the name Ezra. He’s an OJ, and that’s that.'