a Trow is a magical humanoid native to Shetland and Orkney often depicted as small, ugly dwarf-like creatures with a tendency for fairly harmless mischief, though some members were more notably evil in their interactions with humans.
Trow resided in the hills, often underground, though some variants came from the sea (fittingly being known as the Sea-Trow as a result), like many "little people" the Trow could trade with humans despite the often rocky relationship they shared, they also had a fondness for music.
They are very closely related to the trolls (of which they likely evolved from over time, since Shetland and Orkney were once Norse and thus shared much of its mythology and culture, while also growing their own over centuries).
Thus while still considered a regional variant of troll or goblin they are in truth a unique aspect of Shetland and Orkney lore, some theorists used to believe the Trows were inspired by ancient Picts who once inhabited the islands prior to the Viking occupation and were forced into hiding post-occupation, however these theories have never found much weight with mainstream historians and the Trow is thus firmly fixed in fantasy for the foreseeable future.