In the popular mind [standing stones] are usually attributed to the giant race, of whom a faint tradition lingers. It was the giant of Roenis Hill who, in his combat with the giant of Papa Stour, threw a stone at his opponent in the distant island, which fell short and is now known as the Standing Stone of Busta. Similar tales are told of other standing stones.
From p91 of ‘Shetland Folk-lore’ by John Spence (1899).
Ronas / Ronies Hill (the highest point on the island?) is crowned by a chambered cairn. Surely a good spot for a giant to live?