Semantics of the Holiday Season

When did it become such a source of dissonance to say 'Happy Holidays'? My mom corrects me by saying, "You mean, 'Merry Christmas'?" I think to myself <please know that it is a daily struggle not to be sassy...even at my age>, "Well, yes, I mean 'Happy Holidays', 'Merry Christmas, 'Have a great day', or whatever the person to whom I am imparting a blessing may perceive...because that it what it is in essence, a blessing. We each bring different experiences or backgrounds which shape our individual current states of mind. So if someone says 'Happy Holidays' to you, just accept it. They may be coming from a different place than you...and if you want to say Merry Christmas, I won't correct you because I know what you mean. ;)

*Just a note...I love you, Mom.  ;) I know what you mean when you say that I should say "Merry Christmas", and I respect the belief. So to you, "A very Merry Christmas!"  <3 , Me