There is an old tradition that in some Irish houses (although now not many), people put a tall, thick candle on the sill of the largest window after sunset on Christmas Eve. The candle is left to burn all night and represents a welcoming light for Mary and Joseph

In Irish (or Gaelic) Christmas is 'Nollaig', Santa Claus is known as 'San Nioclás' (Saint Nicholas) or 'Daidí na Nollag' (Father Christmas) and Happy/Merry Christmas is 'Nollaig Shona Dhuit'. Happy/Merry Christmas in lots more languages