Ernie Headsize means in slang: He is the type of student who knows everything. Although he is extremely smart, he always tries to learn more than what a student needs. His head size is Ernie. He’s a bit geeky, but not in the Sheldon form of Big Bang Theory way. It can also be used to greet them when they are seen in public. (in Slang Dictionary, added by Yolanda Arias)