IPA: //ˈkɒstəmʌŋɡə//
KK: /ˈkɔstərˌmʌŋɡər/
A person who sells fruits, vegetables, or other goods from a cart or stand in the streets.
The costermonger set up his stall early in the morning to sell fresh produce.
Costermonger is formed from "costard" (from Old French *costarde*, meaning a type of apple) and "monger" (from Old English *mangere*, meaning dealer or trader). The word refers to a dealer or trader of costards, specifically apples.
Think of a 'dealer' ('monger') who sells a specific type of apple ('costard'). This helps you remember that a costermonger is someone who sells apples.