"Dorsetshire Folk-Lore" by John Symonds Udal gives the quote Rhiannon has found, and then goes on:
"To this another correspondent in Notes and Queries (p.187) 'C.W.' - under which initials it is not difficult, I think, to recognize the well-known Dorset antiquary, the late Charles Warne, F.S.A - replies:
"Your correspondent 'C.W.B.' has not aluded to a mythological tradition connected with the 'Giant's Grave' and the stones adjoining it, which is popular in the neigbourhood. It is to the following efect. Two giants standing on Norden (an adjacent hill) were once contending for the mastery as to which of them would hurl the farther, the direction being across the valley to Hanging Hill. He whose stone fell short was so mortified at the failure, that he died of vexation and was buried beneath the mound which has since been known as the 'Giant's Grave'. Myths of a similar kind are often found attached to blocks of erratic stone.""
Every parish in Dorset (and many other parts of the country too) seems to have acquired its own version of this stone-hurling. Sometimes it is the Devil that does the chucking. It's tempting to view this as medieval ignorance but perhaps each succesive trend in superstition going back to ye Stone Age has had its own version. But here it's nice to see the two sites being woven together in one narrative.
There is a long mound in a part of my parish which is popularly called the "Giant's Grave," and very near it two large stones, which have probably rolled down from the beds of chert-like rock on the side or the chalk-hill above. I discovered lately that there is a popular tradition existing, though my informant somewhat doubted its correctness, that these stones move whenever they hear the cocks crow in Chesilborne, a neighbouring village.