Cockney rhyming slang
From Tardis Wiki, the free Doctor Who reference
Cockney rhyming slang was when one word was replaced by another word or phrase that rhymed. Leela noted that it was like a code, when she first learnt about it.
Examples included "boat race" which was slang for "face", "Rosy Lee" for "tea", "apples and pears" as an alternative for "stairs", and "plates of meat" for "feet". (AUDIO: Dead Men's Tales)
