My mother and I went out t eat at a Chinese restaurant that was not in a mall food court. I had MooShi Shrimp plate and my mother Shrimp in Garlic Sauce. Both excellent. Anyways what do I hear from the table next to us? A woman about midthirties telling the man she was with who just came from the bathroom "zipper up". He did though he looked sheepish.
I went to high school in the early eighties and it was a boy's Catholic High School the vice principal would prowl the halls of the school and if he saw one of us unzipped he would say in a loud voice "hey Einstein" of course if we were in his direction we would all look down then look at the one zippering up. Although not surprising sometimes two were unzipped. That phrase caught on quickly with all of us.
I do not know if the term Einstein is regional or unique to that vice principal. But an Einstein is simply a man who forgets to zip his pants. I confess I am guilty of this.
Why does this happen? Its not hard. Laziness? I think because we button our pants shut then buckle the buckle our hands are moving upward not downward thus zipping is forgotten. Best theory I have and I am sticking to it.