Billy to Bob
is a version of The Wren Song
[Hunting the Wren] with chorus. Roud Folk Song Index No. 236
. A recording made by Jack Elliott
can be heard at here
Many think that it represents human sacrifice of the Year King, or the symbolic substitute slaughter of the wren as "king of the birds" at the end of the year for similar purposes, and such songs are traditionally sung on Boxing Day, just after the winter solstice.
This song may be found in the Tyneside Maritime Chorus songbook