When I was a child I was told that to write Xmas instead of Christmas was not appropriate. It was un-Christian and bad. “Xmas” was, the teachers said, an unbeliever's way of having "Christmas" but leaving Christ out.
Today children carry home the same woeful tale. Guess what! It isn't true!
For one thing the X in Xmas isn't really an X. X is the Greek letter chi(ki). It is pronounced like ki is in kitten. The Greek letter X then represents the Greek word Khristos, which is Christ.
So X-mas is really Khristmas or Christmas.
Speaking of Greek, do you know what IXTHUS means? It is the Greek word for fish. So what!? Well, now you may understand why a fish is a well-known symbol of Christianity.
Here is why: the first letter of the Greek word for fish is the first letter of the Greek word for Jesus, (I) Iesus. The second letter X, stands for the word Xristos (Christ). The two letter TH stand for THEOS (GOD). The U stands for the Greek word for Son (Uios). The final letter S stands for the Greek word Savior (soterios).
Put it all together and the letters of the word give this message:
So IXTHUS (FISH) is a symbol of Christianity,