Where did the term "Blue Murder" originate?

"Getting away with blue murder"

Implies a person has gotten away with something so bad that they were expected to get get caught for.
If you a royal was murdered it would be assumed that the culprit would be apprehended as there would be an unusual large manhunt undertaken making getting away with this murder harder than the murder of a normal person. And since royals are known as blue bloods this is were the term originated.

I've seen a couple of explanations, for two different ways the phrase is used.

(1) The murder of royalty, or blue-bloods, was historically exceptionally heinous and difficult to get away with. So if someone "got away with blue murder" they were quite lucky and/or devious indeed.

http://www.answers.com/Q/Where_does_the_expression_%27blue_murder%27_come_from


(2) Then there is the phrase "to scream/howl/cry blue murder", which is to raise an excessive outcry. It comes from the French "morbleu", a rhyming euphemism for the oath "Par la mort de Dieu". "Morbleu" is a corruption of "mort bleu", or blue death, not a great leap to "blue murder".

http://fr.wiktionary.org/wiki/morbleu
http://www.answerbag.com/q_view/54788

In addition to the explanations given above, another use of the French word "bleu" in an exclamation of terror or astonishment is "sacre bleu." This could be another example of euphemisms, as "sacre Dieu" (holy God!) became "sacre bleu." The word "blue" in English also has a history of being used to stress or strengthen an expression, as in "blue funk" or "blue blazes." These could have affected the popularity of the use of "blue" with "murder" in English.

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