Rhyming slang in Glasgow at least is not a new phenomenon.

"Corned beef" for deaf (but it only works if you say "deef") is older than me for sure... And Francie and Josie 40 years ago were calling people "China" - (China Plate - Mate). Also - can confirm that "whit's the Hampden" - "What's the score?" - Hampden Roar/Score has been around for at least 30 years. Some other ones that I've only heard locally, but work perfectly well in English e.g.: "He went Radio Rental" (i.e. mental)(further explanation - Radio Rental = firm providing domestic appliance rental - TV's etc...)

A really weird one is "Ah'm gonny shoot" - "I''m about to depart" - short for "shoot the crow"/go - However, whenever anyone ACTALLY says "Shoot the crow", they inevitably say "Shoot the CRAW" - which does not rhyme at all..

I'm not going to trouble you with racist derivation of "Hamiltons" - short for "Hamilton Accies"..

Regualrly heard is "Gies a coupla Mick Jaggers, eh?" - "WOuld you be so kind as to furnish me with two pints of lager?" - notice that this works in Glasgow, because lager is not pronounced "laaw-ger".

Hope this helps

Cheers

Steven