I was curious about this many years ago and asked around to no avail in the days before the internet. I hoped improvements in communication these days would help. What prompted it now specifically was that I heard the phrase used on TV by a Cockney character, so it is clearly not confined to Glasgow.

Senoufou, I remember the songwriter Bill Hill saying he thought rhyming slang was confined to London until he moved to Edinburgh, then when he spent some time in Glasgow he realised Cockneys were rank amateurs in the practice.