More on Morbleu from Infoplease:

• Morbleu! - Morbleu! (French). A corruption of Mort de Dieu. (See Ventre St. Gris.) Source: Dictionary of ...
• Blue Murder - Blue Murder To shout blue murder. Indicative more of terror or alarm than of real danger. It ...
• Dictionary of Phrase and Fable: M - Definitions, origins, and illustrative excerpts for words, phases, and literary allusions starting with "M"