Toilet humor was the thing in Middle Ages. If your joke didn’t contain any body parts or bodily fluids it had to be really harsh on a public figure or even the royalty, to get a good laugh.
You can read more jokes from the book here.
medieval yo mama joke -
A young Florentine was going down to River Arno with one of those nets in which they wash wool, and met a frolicsome boy, who, out of fun, asked him what birds he was going to catch with that net of his? “I am going to the Brothel’s outlet,” replied the youth, “to spread my net there, and catch your mother.” “Mind you search the place carefully,” retorted the boy, “for you will be sure to find yours there also.”
c. 1880s - (Via)