It has happened to everyone, when you're thinking about what you're going to say, and two options come to mind. When you speak, instead of picking one, you utter a weird/unheard of combination of the two. The possibility of this happening increases when you're telling a story or talking about something you're excited about. This experience happened to me. I was thinking of the phrases "jack shit" and "shit all" and it came out "jack shit all". I know what you're thinking, use that in a sentence right?
In this photo, I appear as if I'm up to no good, but in reality I was doing jack shit all sitting in my car in the Costco parking lot this morning.