I read once that the original cockney rhyming slang terms also created a visual link to the item.
e.g.
Apples & Pears: Stairs -the barrow boys used to stack up the oranges and apples (much like they do in produce sections and "fancy" stores today) and they looked like stairs
Dog&Bone = phone -the old free-standing dial phones with the recever in a cradle on the top looked like a dog ?????....
...... There wasn't any TV to watch in those days
