OK, I got curious so I checked what the Wolfrider's Guide has to say about soulnames.
"A soulname is described as '...a word/sound/concept that expresses a wolfrider's personal individuality (and all that that means). Soul names grow out of the elves' increasingly frequent use of sending as a form of communication, protecting an elf's deepest, private self."
"When a group of elves, such as the Sun Folk or Go-Backs, are unaccustomed to sending, they lose their need for soul names, being able to keep their private selves to themselves."
There's more but it's only about wolfriders...