Brownies are generally helpful household faeries said to sometimes adopt the homes of humans. 

The brownie is known alternatively as Booka (Wales), Bodach (Scotland and Ireland), and Fenoderee (Isle of Man); but regardless of the name or title used, brownies typically appear as small, scruffy men with wrinkled faces, dressed in tattered old clothes. Once a brownie has moved into a house, he will help with the chores, but only at night; while responsible, these faeries prefer to have privacy.  If a human is fortunate enough to have such a guest, then they should reward the brownie's helpfulness by leaving him a bowl of cream or milk and a cake smeared with honey--but take care not to insult the fellow with a gift too fine, for like many of the Fair Folk, brownies are prideful, and don't take kindly to handouts. Treading lightly around a brownie is always good advice, since they are as capricious as any faerie, and are known to repay a slight by playing pranks costly to their human hosts. One story tells of a brownie so angered by a farmer who insulted his mowing that he threw the farmer's entire harvest over a steep cliff.

So if you find your hearth swept, shoes cobbled, butter churned, or similar household duties conveniently and inexplicably done, then make sure to leave out a small meal as repayment before retiring for the night; but don't say thank you out loud or otherwise insult the pride of any nearby invisible ears, lest you drive away the brownie that's been helping you out.