Macbook Pro local hostname changed inadvertently

I woke up to a message window that indicated that "This computer's local hostname "xxxxxxx.local" is already in use on this network. The name has been changed to "xxxxxxx-2.local".

Can anyone tell me how this happened? I have not made any local hostname changes to my macbook pro so I was surprised that it changed. How would I find out where my old local host is being used? It is disconcerting...