The Ballad of Adler Young, Canto 2.5

>you know at this point, you migh as well take Percy with you too, he's annoying but uou have to admire the dedication and persistance, throw him a bone, so to speak. And frankly if you let him in, it's not like he'll last long in faerie anyway.

>(Or you know maybe you could use his lowfolk power of l;ying to your advantage, it's dirty but after the queen tried to get you offed, no mercy)

>If you're feeling particulary mean, you could send him into the swamp, or Vulpitia. Either he'll drive them nuts or they'll.. deal with him. One way or another, problem solved.

while "Frost-Biter" could refer to an incident in Fifi's home village, when she tried learning Cryomancy with disastrous results.

Or y'know, it could just refer to the fact their fur is snow white.
Rabbits are not very imaginative.