A more thorough explanation:

Definition: In ancient Rome, nexi were people who owed money to creditors and were forced into bondage until their debts were paid off. This was known as nexum.

Example: If a person borrowed money from someone in ancient Rome and couldn't pay it back, they could become a nexi. They would be forced to work for the creditor until the debt was paid off. This was a way for creditors to ensure they would get their money back.