Let's look at wish first of all. In your 'Merry Christmas' example, or when you wish someone good luck or Happy Birthday, you are expressing the hope that they will have good luck in the future ...

When I respond “Thank you. Merry Christmas,” I sometimes sense that I have actually created some tension. While many of those to whom I wish “Merry Christmas” may actually be happy that ...

We hope you’ve had a wonderful Christmas morning, and on behalf of the team here, I’d like to wish you a Merry Christmas and Happy Holidays on behalf of the team at The Leafs Nation!