Averill is a surname to me - that's the only way I've seen it. To me it's just not a personal enough name, and seems much like all the other surname names that are trendy -
Emerson,
Avery,
Aubrey etc. Usable, not exactly unpleasant, but nmsaa.
Avril has too much air about it for me.
Avril Lavigne ... it's glammed up. If one doesn't speak French, it seems like the only reason to use
Avril instead of
April is to put on an air.
Everild, though ... that's neat. The D at the end is soft enough - it's not so much a statement as
Astrid or
Mildred or
Ingrid. I could even see dropping it. Everil. I guess then it is a little too much like "ever ill" though. Hm. Evril? I like that. Oh well, you're probably not that creatively inclined anyway.