scavenger?

[Linda Trimm]

Dundee Scotland, 1861, two adult males, both 43,  different surnames, the head of house and a lodger: Scavengers. Three teenage boys, all lodgers with a surname that matches no adults, only other teenagers in house: Millworkers. Why do I get the feeling the census taker was being snide with this?

I'm American though, so no frame of reference for British occupations.