Jesus H. Christ is an example of slang serving as a mild, joking curse. The expression is most commonly used in a wry, sarcastic, cynical, or joking tone, although it may nonetheless be perceived as blasphemy, being a variation of "Jesus Christ". The expression jokingly implies that the "Christ" in "Jesus Christ" is a surname rather than a title ("Christ", meaning anointed, is Greek for "Messiah")
Comically, some people have stated the "H" stands for "Harvey" or "Hubert."