According to Chambers Concise Scots Dictionary, the word gaberlunzie (earlier spelling was "gaberlungy" - please amend Mudcat Scots glossary) dates only from the 17th century, which would rule out the King as composer. I will check the (huge) Scottish National Dictionary in the library later today to see if there are any clues there. The word's origins seem to be lost, Chambers stating that they are "obscure".

PS Jim, photos still safe).