I'm not sure whether the title refers to a penny dropping in Castleblaney or to something sticky. Which ever if the above (or adjacent) is true, the tune seems to have stuck the years OK.
A few years ago a well-meaning but scattered soul taught this title in a class — but I got home and discovered the reason it seemed so familiar was that the A & B parts were really the Ivy Leaf, with the Monaghan Twig C part grafted on. Talk about a hybrid transplantation! Thanks, Michael — maybe now I can untwine the two vines at last. Cheers from your unemployed pal!