Old thread refreshed ~~ because it doesn't seem to answer the thread question in either its 'twictch' or 'switch' version:

I've just been listening to the late great Tommy Makem on youTube singing The Cobbler: "Me father was hung for sheep stealing, Me mother was burned for a witch, Me sister's a dandy housekeeper [presumably euphemism for "bawdyhouse keeper"?] And I'm a mechanical switch".

OK - even allowing a euphemism for "son of a bitch", WHAT does "mechanical switch" mean in the context. We are surely meant to understand something by it!

~Michael~