As John Routledge mentioned in the other thread this ballad was discussed by Nick Caffrey in the Jan/Feb 2002 edition of Living Tradition Issue #46, but the article is not yet available online. However some material from the article and music and sound samples are available at www.thetraditionbearers.com/ballads

The substance of the article is that the ballad is thought to date back to 15th century Scotland, possibly referring to an actual event at some unknown place - with Balwearie in Fifeshire being one of a number of suggested locations.
The name Lambkin or Lammikin is widely agreed by singers of the song to be an epithet which as Child observed "was a sobriquet applied in derision of the meekness with which the builder had submitted to his injury."
Child believed that the original name of the mason was probably Lambert Linkin.

Caffrey notes some of the interpretations of the ballad:-
1. pure revenge
2. ritual sacrifice/ masonic rite
3. Lamkin a symbol of the Devil exacting payment for a bargain
4. Lamkin was a leper, and the bloodletting is a kind of purification/cure
5. ballad is symbolic of revolt against nobility by peasantry

He also notes that the use of a silver bowl to catch the lady's blood has some possible symbolic meanings.