What is the meaning when your friend's boyfriend told you not to tell anyone when you two had just hanged out at your house?

it means that he doesnt think his girlfriend (your friend) trusts him. Or that he's worried that if she finds out she'll talk it the wrong way! He's lying to his girlfriend, your friend and is being sneaky about it. You need not do this anymore, tell him that if you are to hang out it should be only when, your friend is around and out in the open. Why does it have to be a secret. You will wind up loosing a friend if this continues. Is it worth it?