The Collaborative International Dictionary of English v.0.48:

Costermonger \Cos"ter*mon`ger\ (k?s"t?r-m?n`g?r), n. [See
   Costard.]
   An apple seller; a hawker of, or dealer in, any kind of fruit
   or vegetables; a fruiterer. [Written also costardmonger.]
   [1913 Webster]

WordNet (r) 3.0 (2006):

costermonger
    n 1: a hawker of fruit and vegetables from a barrow [syn:
         costermonger, barrow-man, barrow-boy]