The titles of the tunes within Southern Harmony, and Musical Companion sometimes require a bit of history even outside of biblical references. Following are several important relevant facts from the Lazy Person’s Guide to the Universe (Wikipedia) about the meaning of the expression, “The New Jerusalem,” to people in the USA who would have contributed tunes during the time of Southern Harmony.
“The following quotes are from https://en.wikipedia.org/wiki/New_Jerusalem#Universal_Friends.
The New Jerusalem was an important theme in the Puritan colonization of New England in the 17th century. The Puritans were inspired by the passages in Revelation about the New Jerusalem, which they interpreted as being a symbol for the New World. The Puritans saw themselves as the builders of the New Jerusalem on earth. This idea was foundational to American nationalism.
That is the most relevant reference for tunes in Southern Harmony: it’s typical of understanding of American protestant congregational denominations. The term, however isn’t limited to them, it’s also important to the Catholic church and, of course Judaism, as per this quote.
In the Book of Ezekiel in the Hebrew Bible, New Jerusalem (יְהוָה שָׁמָּה, YHWH-shammah, or YHWH [is] there”) is Ezekiel‘s prophetic vision of a city centered on the rebuilt Holy Temple, the Third Temple, to be established in Jerusalem, which would be the capital of the Messianic Kingdom, the meeting place of the twelve tribes of Israel, during the Messianic era. The prophecy is recorded by Ezekiel as having been received on Yom Kippur of the year 3372 of the Hebrew calendar.
There is a LOT more at the Wikipedia link at the beginning of this post. It’s fascinating reading and I highly recommend taking a few minutes to go to the link and travel down a few of the rabbit holes there. My personal favorite was https://en.wikipedia.org/wiki/New_Jerusalem#Swedenborgian. My father, although a Methodist minister, was, nevertheless, an ardent fan of Swedenborg.