Why are street vendors sometimes referred to as `costermongers’?

The word `costermonger’ is mainly used in British English to refer to someone who sells fresh fruit, vegetables and fish on the street. `Monger’ means `seller or trader’; `coster’, on the other hand, is actually a corruption of an old English word `costard’, meaning `apple’. A `costardmonger’ was someone who sold apples on the street.

 Source: ‘Know Your English’ ( The Hindu) -April 23, 2007