Fin is a troll in a legend from Kalundborg, Zealand, Denmark. The legend also exists in Sweden, but it instead has a giant from Lund, with the name Jätten Finn ("Finn the Giant").
Fin (troll) Wikipedia
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.
The troll was strong, and after a few days, there was only a half pillar left to erect before the church would be completed. Esbern became afraid, as the name of the troll was still unknown to him. Wandering the fields in great anxiety, he laid himself down on Ulshøj bank to rest. While there, he heard a troll-woman within the hill singing these words:
Lie still, baby mine! / Tomorrow cometh Fin, / Father thine, / And giveth thee / Esbern Snare's / eyes and heart / to play with.
Esbern returned immediately to the church. The troll was busy setting up the half pillar that remained for the church, and when Esbern saw him, he called out "Fin". The troll was so angry that he threw the half pillar through the air, and this is the reason that the church has only three and a half pillars to this day.
According to the Swedish tradition, when the man (a monk) returned and said the name, Jätten Finn became angry and wrapped his arms around a pillar in order to pull it out and destroy the cathedral. But at that moment he was turned into stone, and that is why there is a stone man hugging a pillar in the Lund Cathedral this day. Another theory is that the carving represents the biblical figure Samson, who sacrificed himself by toppling the pillars of a Philistine temple.