The name originates from the word keeill, meaning chapel. The re-roofed structure contains an important collection of early stone sculpture, including six early Christian cross-slabs, around forty late medieval grave slabs recovered from the chapel or churchyard, and a celtic cross which originally stood outside the chapel where a modern blank replacement now stands. The original has been moved inside the chapel to protect it from the elements.
The complete and well-preserved late 8th-early 9th century cross is carved from local grey-green epidiorite. It is only decorated on one face, the sides and back being dressed smooth without further decoration. Its proportions are unusual, with very short side-arms broader than the shaft and upper limb. The latter shows the archangelSt. Michael standing over a serpent (a symbol of triumph over the devil). The lower limb shows Christ on the Judgement Seat. He is holding a book, possibly the Bible or New Testament, symbolising mercy, in his left hand, and a flail in his right, symbolising judgement. There is a circular design at the crossing, with three round objects in the centre, which may symbolise the Holy Trinity. Around this are four animals representing the four evangelists.