When someone from RCAHMS visited in 1998, they found a low circle of stones here, 15m in diameter. It's been recorded as a cairn, or possible stone circle.
The name.. signifies "The Mountain of the Wild Boar," and the Cantire Highlanders tell the following legend in explanation of the name. Once upon a time, when this mountain was partly clothed with great forests, there lived among them a wild boar of enormous size and strength. He ravaged the country, wandering about for prey, and killing every man and beast that he met. For miles off he could be heard whetting his terrible tusks against the stately oaks, and people were afraid to pass that way, and had to drive their cattle to other pastures. The great hero Fingal came to Cantire, and was told of the wild boar's ravages. Among his brave men there was a mighty hunter named Diarmid, of whom Fingal was jealous and wished to be rid; so to him was committed the dangerous task to slay the boar. Diarmid accepted the task with joy, and set out for the mountain. He entered the oak forest that then grew at its base, and soon got upon the track of the boar. He followed it through the brushwood and the thick hazels that gave to Caledonia its name, and presently heard the boar crunching the bones of a bullock. Diarmid sprang upon him with his spear, but it broke off short in the wild boar's chest, and the beast, maddened with pain and savage anger, rushed upon him. Diarmid stept lightly aside, and the boar, in his blind fury, dashed his tusk against the hard trunk of an oak. Diarmid was instantly upon him with his sword, and plunged it in his bristly body up to the very hilt, and the boar rolled over and died.
Well, this is all very excitingly written but it is rather long, so I feel obliged to summarise the rest (which can be read in full on Google Books).
Diarmid got some help to drag the boar back to Fingal's tent, and people started getting stones for the fire to cook it on, and cracking open the mead or whatever, for a bit of celebration. But Fingal wasn't very happy to see Diarmid back, and one of his muttering supporters suggested there was something a bit funny about Diarmid, and that he was pretty invincible apart from one spot on him.. hmm.. so Fingal called Diarmid over and got him to measure the huge boar by treading across it barefoot.. and then back the other way - but now the stiff bristles of the boar pointed up and pierced his heel; and Diarmid bled to death.
In Glencreggan, by Cuthbert Bede (1861 - volume 2, p7 and onwards).
Perhaps the circle of stones could be where they cooked the boar. Though I expect people's appetites were a bit spoilt by Diarmid's demise.