What does blood in stool mean?

In the medical profession, feces are referred to as stools. This comes from the Anglo-Saxon word stol, which means "seat". The word stool was originally used to describe the seat one sat on to defecate. So, a euphemism was that they were "going to stool". By the end of the 16th century, the word stool was used to mean the same thing as feces.