You need a shave? A haircut? How about a tooth pulled, a bone set, or a lit of blood-letting to restore the balance of your humours? An quick amputation or trepanning?
In medieval times your local barber-surgeon was your one-stop-shop for all those things, and more. A doctor wouldn’t sully his hands with blood or gore (and certainly not with poor people), so a person who knew how to use a sharp blade was a handy person to know.
While doctors went to universities for their theoretical education, the aspiring barber-surgeon was apprenticed to an experienced practitioner for hands on training – dealing with both lather and blood.
As medical science slowly improved, surgeons gradually became more specialised and the two trades parted ways… until we today only have one remaining reminder of the barber surgeon: the traditional red and white barbers pole.