Have you ever read a book where someone says, "Jesus H. Christ!"? I found one recently and like. What the hell does that even mean?

Where does the H come from? Does Jesus have a middle name that I am unaware of?

Update: According to my research, even Wikipedia doesn't know what the everloving crap that means. Urban dictionary says it might be "holy" or "Harold" from "Who art in heaven, Harold be thy name" BUT IT'S NOT HAROLD. IT'S HALLOWED. WHY WOULD JESUS' NAME BE HAROLD.

Good golly, thinking about this makes me want to say Jesus H. Christ! ;)