I am not absolutely certain and I can't find any info by googling etc., but I'm sure my Dad (born 1927, came from South London) used to say he could remember them in the big glass jar in the Chip shop when he was a boy and that they were called Wallys because that was the brand name on the jar (like all vacuum cleaners are called Hoovers). As I say, I have no proof of this, so I could be leading you up the garden path!!