Saint Keyne or Cain[1] (Keane, Kayane[2] Keyna, Cenau, Cenedion,[3] Ceinwen,[4] and ) was a late 5th century holy woman in the West Country, between Liskeard and Looe in SE Cornwall. She is not mentioned as being a saint in the official Catholic encyclopaedia - newadvent.org, so perhaps it's disputable if she is indeed a Catholic saint. The works she is reputed to have done are quite unsaintly, so it is probable that this page is not accurate.
Keyne was a pious virgin, one of the many daughters of King Brychan of Brycheiniog (Brecon). She may havelived at Keynsham in Somerset[5] but founded St Keyne in Cornwall, (among other sites) in the late 5th century, and left her name to a church and to a well, the latter whose waters are said to give the upper hand to whichever of two newly-weds first drinks of them. In 490 she visited her brother Saint Cadoc at St Michael's Mount,[6] where a granite chair (throne?) supposedly is said to grant matrimonial advantage.
She died a virgin on 5 October in either 490 or 505, more likely the later, she ... "grew up to be very beautiful, and many young men sought her hand in marriage, but she rejected them all." Her feast day is also recorded as 30 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 few churches: Llangeinor in mid Glamorgan, Llangunnor and Llangain in Dyfed, at Rockfield (Llangennon) an Runston, in Gwent.[7] ['Llan', in Celtic, means 'Holy Place (of...)'] She is also recorded as being a dragon-slayer, on par with St George.
The plaque next to the well describes the spell which Saint Keyne cast upon the water of the well. The plaque reads: "The legend of Saint Keyne Well. Saint Keyne was a princess who lived about 600 AD. She laid on the waters of this well a spell thus described by Carew in 1602 AD—'The quality that man or wife whom chance or choice attains first of this sacred spring to drink thereby the mastery gains.'"
Her feast is celebrated on 8 October.