What do boys mean by calling you a benefactor?

"Donor" is a Buddhist term that refers to a person who gives property or other material wealth to others. In this context, a boy may call you a "benefactor" because you have given him some help or favor before, so he thanks you in this way.

In addition, it may be because boys think you are rich or have a lot of status, so they use the name "donor" to show their respect for you.

In either case, boys calling you "benefactor" is not a malicious title, but a way to show respect or gratitude. If you don't like this name, you can tell him that you don't like being called "benefactor" and ask him to thank you in other ways.