"The Whummil Bore" is Child ballad 27. A whummil is a tool for drilling holes.
The narrator served the king seven years and "saw his daughter only once" - meaning saw her naked, through a whummil bore. She was being dressed by her maids.
Only one variant of this ballad exists. "Hind Horn" appears to contain a stanza from it.
This is recorded on the Steeleye Span 2006 album Bloody Men.