A very talented writer I know did this piece for Salon about the origins of the Tooth Fairy. It's an interesting read that I thought any GT parents in particular might enjoy.
What Wells discovered in her initial research was striking. Despite the seeming timelessness of the character, the tooth fairy is in fact an extremely recent arrival on the mythological scene. Her first print appearance is an eight-page playlet for children by Esther Watkins Arnold from 1927, and the oldest oral references date her to approximately the turn of the 20th century. By the time Wells started poking around, this supposedly immortal figure was barely even a senior citizen.