What’s the origin of the phrase ‘Plates of meat’?
This is a well-established example of Cockney rhyming slang. The first use of it that there is a record for is a piece in a 1887 edition of Referee:
“As she walked along the street With her little ‘plates of meat’, And the summer sunshine falling On her golden ‘Barnet Fair’.”
The ‘feet’ rhyming slang meaning was preceded by another rhyming word - ‘street’. This is cited in Ducange anglicus, 1857 a reference work with this very specific sub-title - The vulgar tongue: comprising two glossaries of slang, cant, and flash words and phrases, principally used in London at the present day. This lists ‘Plate of meat, street’.