1705. [Mamre was] brother of Eshcol and brother of Aner, and these were men bound by a pact with Abram symbolizes the state of his rational self (or of its outward part) and the nature of its goodness and truth. This can be seen from the symbolism of these men, which will be discussed below at verse 24 where they come up again [§§1753-1754].
To put it briefly, Mamre, Eshcol, and Aner represent and symbolize the angels present with the Lord during the battles of his early youth, who were suited to the goodness and truth he then possessed. They are named for the individual varieties of goodness and truth in him. Angels in heaven never have any names; it is on the basis of their goodness and truth that names are applied to them. Michael and other angels named in the Word, for instance, never go by those names; the names are based on the function they perform, whatever it is. 1
The same is true of Mamre, Eshcol, and Aner here, but in a representative way.
Footnotes:
1. Swedenborg says a little more about names below in §§1754, 1876. In his 1771 work True Christianity 300, he explains, "In [the spiritual] world, people all stop using the names they were given in baptism in this world and the names they received from their parents or their family. All there are named for what they are like." See also Secrets of Heaven 144. [LHC, SS]