Board Thread:Suggestions forum/@comment-26897694-20151007002712/@comment-26236093-20151007121830

TheDwarvenGuy wrote: That part of the hobbit film wasn't canon, and he was probably named that because his shield was made of oak, and not an oak log.

The appendices gives the following foot note on this topic...

It was said that Thorin's shield was cloven and he cast it away and he hewed of with his axe a branch of an oak and held it in his hand to ward off the strokes of his foes, or to wield as a club, in this way he recieved his title