Jaja ja. .. I Am still laughing. Though it would have been interesting to have one tooth fairy.
Another example of this tannf'é is that of Viglundar saga ch 14, where he also gets a ring.
Fritzner defines it as "hvad barnet faar som gave i unledning af den forste tands."
As for snakes, it is well known that they do not mix well with gold, as they grow and grow and become  nasty venom spitting dragons. There are also several examples of this in J Simpsons "folktales of Iceland" (A translation of Jon Arnasson's collection) that has been just reedited.
 
Cheers
 
Fernandur