The idea of blood chit originates from 1793 when French balloonist Jean-Pierre Blanchard demonstrated his hot air balloon in the USA. Because he could not control the direction of the balloon, no one knew where he would land. Because Blanchard did not speak English, George Washington gave him a letter that said that all US citizens were obliged to assist him to return to Philadelphia.

In World War I, British Royal Flying Corps pilots in India and Mesopotamia carried a “goolie chit” printed in four local languages that promised a reward to anyone who would bring an unharmed British aviator back to British lines. The term “goolie” is British slang for “testicles” and was so called (and still is called by the Royal Air Force) because, in the areas where the chits were used, local tribesmen were known to turn over aviators to their womenfolk, who castrated said pilots for use as servants.

via Blood chit – Wikipedia, the free encyclopedia.