Vitamin K

Vitamin K was discovered as a fat-soluble vitamin essential for blood coagulation after observing hemorrhages in hens on certain diets. Dam named it K for koagulation, the German spelling of the word. Doisy worked out the structure of the vitamin and synthesized it.
 Carl Peter Henrik Dam and Edward Adelbert Doisy Denmark and United States 1939 Vitamin K

Vitamin K was discovered as a fat-soluble vitamin essential for blood coagulation after observing hemorrhages in hens on certain diets. Dam named it K for koagulation, the German spelling of the word. Doisy worked out the structure of the vitamin and synthesized it.