Hostname of mac changed? That normal?

Im up at school and i got a pop up saying that my host name was changed..

for example it was john.smith macbook2 and it changed to john.smithmacbook 3

i dont know why. It said that someone else had that name. I realized my bluetooth was on so i shut that and i shut file sharing..

can someone explain why that would happen?

Thanks

 

Ok. Good. So then i shouldnt have to worry! Thanks!