Jesus H. Christ is an example of slang

Slang

Slang is the use of informal words and expressions that are not considered standard in the speaker's language or dialect but are considered more acceptable when used socially. Slang is often to be found in areas of the lexicon that refer to things considered taboo...

 serving as a profanity

Profanity

Profanity is a show of disrespect, or a desecration or debasement of someone or something. Profanity can take the form of words, expressions, gestures, or other social behaviors that are socially constructed or interpreted as insulting, rude, vulgar, obscene, desecrating, or other forms.The...

.

The expression dates to at least the late 19th century, although according to Mark Twain

Mark Twain

Samuel Langhorne Clemens , better known by his pen name Mark Twain, was an American author and humorist...

 it was already old in 1850.

Using the name of Jesus Christ as an oath has been common for many centuries, but the precise origins of the letter H in the expression Jesus H. Christ are obscure. While many explanations have been proposed, some serious and some not, the most widely accepted derivation is from the divine monogram

Christogram

A Christogram is a monogram or combination of letters that forms an abbreviation for the name of Jesus Christ, traditionally used as a Christian symbol. Different types of Christograms are associated with the various traditions of Christianity, e.g...

 of Christian symbolism. The symbol, derived from the first three letters of the Greek

Greek language

Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...

 name of Jesus , is transliterated iota-eta-sigma: IHS, (with lunate sigma), JHS or JHC. Since the transliteration IHS gave rise to the backronym

Backronym

A backronym or bacronym is a phrase constructed purposely, such that an acronym can be formed to a specific desired word. Backronyms may be invented with serious or humorous intent, or may be a type of false or folk etymology....

 Iesus Hominum Salvator (Latin for "Jesus, savior of men"), it is plausible that JHC similarly led to Jesus Harnaldo Christ, Harold coming from the mispronunciation of the word "hallowed" of the Lord's Prayer

Lord's Prayer

The Lord's Prayer is a central prayer in Christianity. In the New Testament of the Christian Bible, it appears in two forms: in the Gospel of Matthew as part of the discourse on ostentation in the Sermon on the Mount, and in the Gospel of Luke, which records Jesus being approached by "one of his...

: "Our Father who art in heaven hallowed be thy name." The H has also been said to stand for "Holy."

External links

• Why do folks say "Jesus H. Christ"?, from the Straight Dope
  Straight Dope
  The Straight Dope is a popular question-and-answer newspaper column published in the Chicago Reader, syndicated in thirty newspapers in the United States and Canada, as well as being available and archived at the .-Newspapers:...
  
   (inconclusive)
• Explanation from WorldWideWords by Michael Quinion (supports the IHC theory)
• Harold be thy name! (has an interesting connection to Epistle of Barnabas
  Epistle of Barnabas
  The Epistle of Barnabas is a Greek epistle containing twenty-one chapters, preserved complete in the 4th century Codex Sinaiticus where it appears at the end of the New Testament...
  
  (9:6-7) (written between 70 and 190 AD) which says "The eighteen is I (=ten) and H (=8) -- you have Jesus".