What is the origin of the idiom "out for blood" and when to use it?

The origin of the idiom "out for blood" can be traced back to a literal interpretation of the phrase. In ancient times, especially in battles or hunting scenarios, people would often be "out for blood" when they were pursuing an enemy or hunting for prey. The phrase likely evolved over time to describe someone who is relentlessly pursuing a goal, often with a strong desire for vengeance or success. It's often employed in competitive or confrontational situations, such as sports, business negotiations, or personal conflicts, to emphasize the person's strong and aggressive resolve to achieve their objective.