Another colloquialism gone awry

One of the most amusing parts of my job is reading what people think typical colloquialisms actually say. Yes, we all know the ones like for all intensive purposes. But what about don't lick a gift horse in the mouth or Chester drawers instead of chest of drawers? 

Today's is more subtle, but it entertains me nonetheless. The phrase is for Christ's sake. As in, for the good/advantage/wellbeing of Christ. It's not for Christ Sake. 

Given the capitalization, I can only assume that whatever we're doing is not for the good of Jesus Christ; it is to obtain a specific brand of fermented rice alcohol.