Vitamin K

 Vitamin K was discovered in 1929 as an essential nutrient for blood coagulation. The initial discovery was reported in a German scientific journal, where it was called “Koagulationsvitamin” — which is where the "K" comes from. 

 

It was also discovered by the dentist Weston, who traveled the world in the early 20th century studying the relationship between diet and disease in different populations. He found that the non-industrial diets were high in some unidentified nutrient, which seemed to provide protection against tooth decay and chronic disease. He referred to this mystery nutrient as “activator X,” which is now believed to have been vitamin K2.