The story of rickets leading to the discovery of vitamin D is an extraordinary tale, spread over many centuries and involving some remarkable characters with much speculation and a few mysteries, before reaching an exciting climax. It would be wrong to credit a single person as discovering rickets or being the first to describe its features, for reasons that will be set out here. Yet the emergence of the term 'rickets' is as important as the discovery of vitamin D itself and the possible causes of its deficiency. It permitted identification of a hitherto ill-defined disease entity, typically occurring in infants and children. It also provided a way for deciding if features of diseases that had been described earlier in the history of medicine could be seen as the symptoms and signs of related conditions.