St Lythans is also known as Gwal y Filiast – the greyhound bitch’s kennel. Maybe the greyhound comes from stories about Ceridwen: themodernantiquarian.com/browse.php?site_id=2234
The cromlech stands in cursed field, where nothing is supposed to be able to grow.
It’s also known as ‘Maes y felin’ – the mill in the meadows. Perhaps this is because the capstone spins round three times on Midsummer’s Eve, like a millstone? “Old people in the beginning of the 19th century said that once a year, on Midsummer Eve, the stones in Maes Y Felin field whirled round three times and made curtsies; and if anybody went to them on Hallowe’en, and whispered in good faith, it would be obtained. The field in which these stones stand was unprofitable, and people said the land was under a curse.” (Marie Trevelyan, Folk lore and folk stories of Wales, 1909 ).