The carols that you sing

[snopes]

http://www.dfw.com/mld/dfw/news/opinion/16306724.htm

Beloved carols from childhood, when heard in later years, bring a smile and a fond memory of how, perhaps, the lyrics were misheard by young ears and came out mangled from little mouths.

There's even a word for misheard Christmas lyrics: mondegreens. According to the online source for myth-busting, snopes.com, the word is generally attributed to Sylvia Wright, who used it in a 1954 Harper's column after she discovered she had long misheard the first stanza of the Scottish folk ballad The Bonny Earl of Murray.