Who were the "gongfermors"?

A gong farmer (also known as a gongfermor or gongfermour), was the term used in Tudor England for someone who removed human excrement from privies and cesspits – the word "gong" was used for both a privy and its contents. Gong farmers were only allowed to work at night, and the waste they collected, known as night soil, had to be taken outside the city or town boundary. A text of 1562 states that "no Goungfermour shall carry any Ordure till after nine of the Clocke in the night.

https://en.wikipedia.org/wiki/Gong_farmer

These gongfermors were more than often young boys, as it was their misfortune to be small enough to crawl along the drains.