bad blood

Anger or animosity, between individuals or groups. The blood was long regarded as the seat of human emotion, and by the sixteenth century it was particularly associated with high temper and anger. “To breed bad (or ill) blood” meant to stir up hard feelings. In the late eighteenth century both Jonathan Swift in England and Thomas Jefferson in America wrote of ill blood in this way, and a few years later the English essayist Charles Lamb wrote of bad blood.