Not everyone says it. I just say it cuz i cant be arsed to type in christmas all the time. Oh and btw havnt you heard the song by Avid Merrion, Proper Crimbo. Well if you live outside the UK you probably havn't.
Proper crimbo SELECTA! lol - that guy is ace! I think people in the U.K say Crimbo as a shortened work for christmas like you have already said. I say Crimbo alot. Sorry!
let me educate you and this is slightly off topic so forgive me but: Bo'slecta is a programme with a man who dresses up as shilebrities by putting a mask over his face. Three series running. I'll find a link lol