St. Keyne’s Well is dedicated to the saint of the beautiful and pious virgin of that name, and originated in the late 5th century. She was the daughter of King Braganus (Brechin) and aunt of King David.
She died a virgin on the 5th October in either 490 or more likely 505. Her feast day is also recorded as 30th September. The Celtic harvest festival was driven more by sun and moon than by an otherwise proscribed calendar. She was the original patron of what is now St Martin's-by-Looe and is linked with Kenwyn in Truro. She is known to have founded a number of churches: Llangeinor in mid Glamorgan, Llangunnor and Llangain in Dyfed, at Rockfield (Llangennon) and Runston, in Gwent.
Interestingly, she is also recorded as being a dragon-slayer, on par with St George.
For further information, please read Haunted Britain by Antony D. Hippisley Coxe.