Google’s NGram Viewer allows anybody to create quick graphs showing word and phrase frequencies in books going back to 1800. The tool searches a database of words from over 5 million books, and you can filter for American English, British English, English fiction, Chinese, French, German, and Russian.
Although it has its restrictions, such as not giving us accurate information about spoken usage, it’s a great analysis tool. One of the Wall Street Journal’s blogs did a Christmas analysis to see whether the PC phrase ‘Happy Holidays’ has infiltrated the world of books. A quick graph generation later, and it seems that ‘Merry Christmas’ is still way out in front. It also seems that around 1900, people started capitalising the ‘merry’.
When I filtered for British English only, it seems that ‘Happy Holidays’ is almost never used. The tool is case sensitive, though, so there has been some use of ‘happy holidays’, but these could have been in more general sentences, rather than as a greeting. In British English, ‘h/Happy Christmas’ is much more common than in American English, and ‘happy Christmas’ was almost as popular as ‘Merry Christmas’ at a few points in time. It seems that the use of ‘happy Christmas’ is on the decline recently, though.
In other Christmas-related news, while Father Christmas and Santa Claus are about equally popular in British literature (and both much more popular than the Easter Bunny), American literature uses Santa Claus almost exclusively (with Father Christmas being about as common as the Easter Bunny).