Barrow boy is a term that has different meanings. In British slang, it refers to a street seller of fruit, named for the wheelbarrow often used to transport the fruit. In this context, a barrow boy is also referred to as a costermonger. The term barrow boy has been used in a mildly derogatory way in the financial industry to refer to voice broking traders, who may not be highly educated.
In British mountain rescue terminology, a barrow boy is the person who guides a stretcher during a crag (steep rugged mass of rock) rescue. Conventionally there are two barrow boys, one at each end of a horizontal stretcher (though it may be vertical) which may contain a casualty. The barrow boys may operate on fixed or moving ropes, and guide the progress of the stretcher to safer ground.
In more generic terms, a Barrow boy may also refer to a boy from a place called Barrow.