Some say that the house had an ominous reputation as a hideout for highwaymen who preyed on unwary travellers. Others say that the house got its name from the rough boulders that comprise its walls and chimney, as the Welsh word hyll can mean crude as well as ugly.
Still others say that the house was never considered ugly, and the name is a corrupted, back-translation of the name of the nearby river, the Llugwy, which sounds like the word ugly to an English ear.
These days, the house is in the care of the Snowdonia Society. They have a lovely tearoom, and sell the honey from several beehives in the gardens.