Sacrebleu is a very old French profanity meant as a cry of surprise or anger.
The expression today is not used in the major French-speaking countries France, Belgium, or Switzerland, but in the English-speaking world, it is well known from Agatha Christie's books about the fictional Belgian detective Hercule Poirot.
Most French dictionaries state "sacrebleu" to be equivalent to "sacredieu". An equivalent English phrase is a minced oath such as "gosh darn it" (for "god damn it") where the strong religious terms are euphemized, like the term bleu in the French curse.
The origin may go back to the time of Moses, when in Numbers 15:37-40 he was instructed by the Lord to have the children of Israel put a blue thread in the tassels of the corners of their garments "that you may look upon it and remember all the commandments of the Lord and do them".
Other sources propose it coming from old blasphemous curses relating to God, used from the late Middle-Age (some are attested as early as the 11th century) to the 14th (at the latest), with many variants: morbleu or mordieu, corbleu, palsambleu, jarnidieu, tudieu, respectively standing for mort [de] Dieu (God's death), corps [de] Dieu (God's body), par le sang [de] Dieu (by God's blood, the two latter possibly referring to the Eucharistic bread and wine), je renie Dieu (I deny God), tue Dieu (kill God)... Those curses may be compared to the archaic English [God']sdeath, sblood, struth or zounds (God's wounds). They were considered so offensive that Dieu was sublimated into the similar sounding neutral syllable bleu. The verb sacrer has several meanings, including to crown, to anoint, to name someone [champion, best actor, etc.], and in the past, rarely in France but more common in French Canada, of swear, curse. Therefore, sacrebleu could be in modern French Je jure par Dieu and in English I curse by God, or the more used I swear to God.
- SACREBLEU : Etymologie de SACREBLEU
- Johnson, Kevin Orlin (1994). Why do Catholics do that?. Ballantine Books. ISBN 0-345-39726-6. Chapter 32
- Tassie, J. S (1961).” The Use of Sacrilege in the Speech of French Canada”, American Speech, 36.1
- Dictionnaire étymologique, éditions France Loisirs Librairie Larousse 1971