freeze your blood fill you with feelings of fear or horror.

☞ According to the medieval physiological scheme of the four humours in the human body (melancholy, phlegm, blood, and choler), blood was the hot, moist element, so the effect of horror or fear in making the blood cold was to make it unable to fulfil its proper function of supplying the body with vital heat or energy. Compare with make your blood run cold (atblood).