Brownie

Webster's Dictionary

(n.) An imaginary good-natured spirit, who was supposed often to perform important services around the house by night, such as thrashing, churning, sweeping.

The Nuttall Encyclopedia

A good-natured household elf, believed in Scotland to render obliging services to good housewives, and his presence an evidence that the internal economies were approved of, as he favoured good husbandry, and was partial to houses where it was observed.