A more thorough explanation:

custos

Custos is a Latin word that means a keeper, protector, or guardian. In history, custos was used to refer to a person who was responsible for taking care of something or someone.

• The custos of the museum was in charge of protecting the valuable artifacts.
• The custos of the castle was responsible for guarding the king's treasure.
• The custos of the library was tasked with keeping the books safe and in good condition.

These examples illustrate how custos was used to refer to a person who had the responsibility of protecting and taking care of something valuable or important.