The first modern flushable toilet was invented in 1596 by Sir John Harrington who installed one for his godmother, Elizabeth I.
Occasionally, some brave knights would conduct sneak attacks by entering the castle via the shaft connected to the garderobe. Throughout history, there have been a number of famous people who died on the toilet. Several of them were stabbed from below while in the process of defecating.
These people include King Edmund II of England (30 November 1016), Jaromír Duke of Bohemia (4 November 1035), Godfrey IV Duke of Lower Lorraine (circa. 26-27 February 1076), Wenceslaus III of Bohemia (4 August 1306) and Uesugi Kenshin (19 April 1578).
In some cases they had serves who's job it was to clean the area under the pooper
Human waste can also be used in tanning leather so it might have been reused for that