Puritan Board Junior
He gives many reasons, but I think the primary gist of it is that the "Sabbath" is properly the name God gave to the seventh day, whereas the "Lord's Day" is the name given by God to the first day (he pulls strongly off of John's use of the phrase in Revelation, as something the churches obviously were familiar with and used otherwise it would have been confusing to use the term). He also cites from many of the early church fathers who use the term "Lord's Day" as something in common use since antiquity.I call Sunday "the Lord's day." Why does he recommend it, and is this as opposed to calling Sunday "the Sabbath"?
He also states that Satan doesn't like this term because it causes people to inquire why it is call "the Lord's Day", and says that if we were to get back to calling it that, then it would be a great help to people's observation of it, to think about it in those terms.
It seems to be a variant of taking "sola Scriptura" very literally, seriously, and perhaps extremely: Scripture doesn't call it "Sunday" so we shouldn't. And Scripture doesn't call the other days by the names of planets, but calls them the "second, third" and so forth, so we should too. Whether it was a good idea or not, I don't think it really caught on