wwh:

I accessed your link. Here's what was there:

bole (n) Stem of a tree. Scan => ME bol, Ice bolr, bulr (the trunk of a tree), Swe bål, Dan bul.

Stem of tree? I never heard of a trunk being referred to as a stem...though later in the definition there's bulr (the trunk of a tree).

Bulr makes me think of burled oak, but I don't expect there's a connection...

Bole regards,
Woodsworth

Edit/Addendum: A little more on burls (as in burled oak):

Function: noun
Etymology: Middle English burle, from (assumed) Middle French bourle tuft of wool, from (assumed) Vulgar Latin burrula, diminutive of Late Latin burra shaggy cloth
Date: 15th century
1 : a knot or lump in thread or cloth
2 a : a hard woody often flattened hemispherical outgrowth on a tree b : veneer made from burls