I was, um, "researching" on Wiki and you'll never guess what I came across at the bottom of the entry on
Satyrs. It said: See also: Glaistig - Scottish. Glaistig? GLAISTIG???!
You can read the entry itself
here. It appears The Stig, I mean, The Glaistig is a lady-faun who conceals her goatish legs with a racing suit with long flowing green robes. She has "dusky or grey skin and long blonde hair".
This site tells of The Glaistig in local Scottish folklore:
In the village of Ach-na-Creige on the Isle of Mull, a Glaistig served as the guardian of the local cattle. It was customary to pour some milk into a holed stone on the cattle fold as a libation to the Glaistig. This small token was the only payment she requested for her long vigils. A local herds boy - who was widely known for his mischief - decided he was going to have some fun at the Glaistig's expense, and poured boiling milk into the holed stone. The Glaistig severely scalded her tongue, and was so angry that she left the local countryside, and her wardenship of the village cattle for good.
So perhaps this is the truth that The Stig conceals behind his (or her??) helmet and racing suit! Perhaps Richard Hammond (and sometimes James May) is not the only half-goat member of the Top Gear team. Perhaps, after those cheeky bastards scolded her tongue, The Glaistig left bonny Scotland behind to pursue her lifelong dream to be a racing car driver - but she had to maintain her anonymity because of her non-human status. So she dropped the 'glai' part of her name and hid behind the dark visor of her helmet.
I anticipate further proof in form of manips and fics to be forthcoming.