Ok Greg so my da was using the term (so he told me)when he was a lad in the 1920's (and his da before him in the 18 sumits)to mean a "tune session" if you added singing (and possibly some dncing) then it became a ....(wait for it) .... a Celidh. So do I win on the historical precedence bit?

However non of this alters the fact that the usage has changed, quicker than our understanding has, so we have to accept it.