[tflabo]

The X-mas is very insulting. Similar to sending a birthday card to family or friend with the title ‘Happy Birthday X.’
Keep Christ in Christmas.

[donna]

The "X" in Xmas is from the Greek letter Chi, which is the first letter of Χριστός, Christ in Greek.

[VRWCmember]

In notetaking, a capital X is often used as an abbreviation for Christ. In fact in the Greek acronym ΙΧΦΥΣ, transliterated "Ichthus", and often seen inside the the outline of a fish, the letter Chi (X) stands for Christ. So even when people use the abbreviation X-mas, they still haven't really taken Christ out of Christmas.