What does the "H" stand for, as in Jesus H. Christ?
I like to think it was for Henry. My grandfather‘s name was Henry and he was a tough old bastard. So maybe Jesus was a tough old bastard, Jesus H Christ that sounds pretty tough to me. My grandfather couldn’t walk across water but if you pissed him off he sure as hell could run across it to catch your ass.
Here, a possible origin is the name "Harold"; which indeed is mentioned by Smith (1994:32) as the basis of a variant form, "Jesus Harold Christ". The "Harold" may arise from a common misinterpretation (often by children) of the phrase in the Lord's Prayer, "Our Father who art in heaven hallowed be thy name."