Literally, just someone who likes elves. This phrase means drastically different things depending on when it was used. After the publication of Tolkien's "The Lord of the Rings", this meant someone who liked the style of elves present in fantasy novels, and is a fairly common concept in modern fantasy. What we're talking about here is the older meaning, especially as it relates to Spruce Street.
Several prominent mystics in the Clark County area identified themselves as Elf-Friend. Aethelwyne is the most famous, but Allenora and Aembersyne are also documented as using the moniker. The exact meaning is a bit unclear, but the gist seems to be that they believed themselves to be in contact with an immortal, beautiful race of perfect beings. The multiple authors who have taken on the persona of Aethelwyne attempt to portray as one immortal being, but textual analysis reveals that to be false. Similarly, the experiences of other Elf-friends seem to indicate how dangerous believing yourself to be immortal can be to your actual lifespan.
- Randy Jameson, "A Spruce Street Glossary"