Cockney idiolect (7,5)
I believe the answer is:
rhyming slang
(Other definitions for rhyming slang that I've seen before include "Titfer, butcher's and porky, for example" , "Cockney idiom" , ""Apples and pears" for stairs, for example" , "Eg "apples" for "stairs"" , "Cockney poetical chatter" .)