Some people use Xmas as shorthand for
Christmas, the abbreviation is not modern and was not invented for
the purpose of being disrespectful to Christians. It is not supposed
to eliminate the word “Christ” and the X is not meant to stand for
anonymity. The X is actually considered to represent the letter Chi
from the Greek alphabet, the first letter in the word Christos. The
“-mas” part on the end of Christmas and Xmas comes from the Old
English word for “mass”.
Xmas is sometimes pronounced xmas, but it and variants such as Xtemass, originated as handwriting abbreviations for the typical pronunciation of Christmas. There is a common misconception that the word Xmas stems from a secular attempt to remove the religious tradition from Christmas by taking the 'Christ' out of 'Christmas', but its use dates back to the 16th century.
In the United States, in 1977 New Hampshire Governor Meldrim Thomson
sent out a press release saying that he wanted journalists to keep
the 'Christ' in Christmas, and not call it Xmas, which he called a
pagan spelling of Christmas. Many of those who dislike abbreviating
the word are unfamiliar with a long history of Christians using X in
place of 'Christ' for various purposes.
The word 'Christ' and its compounds, including 'Christmas', have
been abbreviated in English for at least the past 1,000 years, long
before the modern "Xmas" was commonly used. Christ was often written
as "Xρ" or "Xt" as far back as 1021. This X and P arose as the
uppercase forms of the Greek letters χ (Ch) and ρ (R) used in
ancient abbreviations for Χριστος (Greek for Christ), and are still
widely seen in many Eastern Orthodox icons depicting Jesus Christ.
The two Greek letters shown as ☧, is a symbol often used to
represent Christ in Catholic, Protestant, and Orthodox Christian
Churches. Bottom Line; it was once positive to use xmas, but has
now become bad form to use anything but Christmas.