Apocalypse Revealed#860
860. Whose number is as the sand of the sea. This symbolizes the multitude of such people.
The multitude of such people is likened to the sand of the sea, because the sea symbolizes the external component of the church (nos. 402-404, 470), and the sand is something which serves no use in the sea except to compose the bottom.
Because the number of such people is so great, therefore the valley of their burial is called "The Multitude of Gog," and the name of the city where they are, "The Multitude" (Ezekiel 39:15-16).
Apocalypse Revealed#196
196. "'Also My new name.'" This symbolizes worship of the Lord alone, with new elements that did not exist in the prior church.
To be shown that the Lord's name symbolizes everything by which He is worshiped, see no. 81 above. Thus it means here worship of the Lord alone, with new elements that did not exist in the prior church.
That worship in the New Church will be worship of the Lord alone is apparent from chapter Revelation 21, verses 9 and 10, where this church is called the Lamb's wife.
That this church will have new elements in it is apparent from chapter 21:5, where we are told, "Behold, I make all things new."
This is therefore the symbolic meaning of "My new name" which will be engraved on them.