What is "barnstokkr"

In Norse mythology, Barnstokkr ( Old Norse, literally "child- trunk") is a tree that stands in the center of King Völsung's hall. Barnstokkr is attested in chapters 2 and 3 of the Völsunga saga, written in the 13th century from earlier tradition, partially based on events from the 5th century and the 6th century, where, during a banquet, a one-eyed stranger appears and thrusts a sword into the tree which only Sigmund is able to pull free. Scholarly theories have been put forth about the implications of Barnstokkr and its relation to other trees in Germanic paganism.