Fin is a troll in a legend from Kalundborg, Zealand, Denmark. The legend tells how Esbern Snare was building a church in Kalundborg. It was hard work, and a troll, who was passing by, offered his services. Esbern accepted; however, the troll's condition was that Esbern should be able to figure out the troll's name by the time the church was finished; if he could not, the troll would take his heart and his eyes.
en.wikipedia.org/wiki/Fin_(troll)
Awww, don't stop there! I wanna hear the rest of the story!
What? I didn't read it, just copied&pasted the text. Let's see... Seems like the guys who wrote Rumpelstiltskin stole the idea from that legend. Guess this Esbern guy finds a magic way out, a deus ex machina(e) type of thing, like a fairy appearing and wreaking havoc.
Damn fairies! Always wrecking my stories 
Actually, he hears the trolls wife talking to the trolls baby about how the baby will get some new toys the next day (the new toys being the guys eyes).