It is worth noting that likely this idea entered medicine back in the old days, like, before this century.
You could read some work by Charles Dickens and it would say something like, "He was of a strong constitution." Made up of strong stuff.
A lot of the verbiage in the notes has this sort of old-fashioned feel, I call it the voice of the "gentleman scientist."
When I think of constitution and the "humors' in this way, it's a bit easier for me to remember what the constitutional symptoms are and to ask about them.