The coincidence suggests “merry Christmas” was already common enough parlance in the era, or at least familiar enough that the readers of 19th century England would know what it meant.

It's just fine to say 'Merry Christmas': Most Canadians prefer it to 'Happy Holidays,' poll finds Even 92 per cent of respondents who grew up in a non-Christian household said they are not ...

I talked to a bus driver about this. He said that Saskatoon Transit management programmed the bus signs to give drivers the option of having a “merry Christmas” message.