A brownie or broonie (Scots), also known as a brùnaidh or gruagach (Scottish Gaelic), is a household spirit or hobgoblin from Scottish folklore that is said to come out at night while the owners of the house are asleep and perform various chores and farming tasks. The human owners of the house must leave a bowl of milk or cream or some other offering for the brownie, usually by the hearth. Brownies are described as easily offended and will leave their homes forever if they feel they have been insulted or in any way taken advantage of. Brownies are characteristically mischievous and are often said to punish or pull pranks on lazy servants. If angered, they are sometimes said to turn malicious, like boggarts.

https://en.wikipedia.org/wiki/Brownie_(folklore)