From the ads in the back of old comic books--where you could deliver _The Grit_ newspaper, and if you sold enough subscriptions you could win a vast array of crappy prizes. Someone who lacks talent or potential. Example: Someday, my manager could grow up to be a grit newspaperboy.
GRIT NEWSPAPERBOY
Meaning of GRIT NEWSPAPERBOY in English
Slang English vocab. Английский сленговый словарь. 2012