Questions about "God Rest Ye Merry, Gentlemen"

The couplet you refer to is: This holy tide of Christmas All other doth deface. This means: 'The holy time of Christmas surpasses/wipes out/replaces all others.' 'Doth' is part of the verb 'to do' (3rd person singular, in this case ... as: 'I do', 'Thou dost', 'He doth', 'We do', 'You do', 'They do'. It is an old English form which was current in the 17th Century and had actually gone out of use in 1833, when the song was written. Here it is used because the writer wanted to give a religious and 'old' feeling to the song by using the language of the King James' bible and the prayer book. 'Deface' means, literally, to damage a picture or a statue by destroying the face of the person depicted. It can also mean making money (or something valuable) worthless because coins usually carried the face of the emperor and to damage that image was considered sacrilege. In this case, the writer is using the word rather loosely because, I suspect, it rhymes with 'place'!