Hi, Jo here. One of the things I like most about writing is the unexpected things I come across when doing research.
Antimony sounds to me like a musical term or a concoction, but it's actually an element. Sb. (A good one for a quiz where they want elements that don't end with -ium.) It's also a metalloid, which means it's a sort of metal but not quite. Bear with me -- a chemist, I am not!
It has a number of uses, one of which is medical, which is where I stumbled across it. Treatments using antimony are called antimonials and they are used against some parasites, and have been for a long time, even before microbial parasites were known. In the past a lot of medicine was trial and error and antimony is also an emetic and laxitive. Anything that caused a dramatic expulsion of bodily fluids and matter was seen as "getting rid of toxins." If the illness was caused by some parasites the patient might get better, then it would be attributed to expulsion of toxins.