[Fred Mertz]

It's axiom. What's a blue murder? I'm serious.

[Chad Fairbanks]

To shout blue murder. Indicative more of terror or alarm than of real danger. It appears to be a play on the French exclamation morbleu; there may also be a distinct allusion to the common phrase “blue ruin.”

[nopardons]

" BLUE MURDER " is part of a VERY old phrase ... as in " CRYING BLUE MURDER ." An IDIOMATIC / POETIC term. I really did NOT mean to confuse anyone. SORRY. : - (

I really can't explain it further, unless I go look it up. It's just something I grew up hearing. It REALLY is good / correct English ; or used to be.

[nopardons]

Sorry for the typo. Thanks for the corection. : - )