K'el-- first thing I thought of are the winding shapes of Celtic design-- wonder if those words are related, I don't know what "Book of Cels" really means.
The Book of Kells is named so for the cathedral at Kells, County Meath, in Ireland.
"An Irish manuscript containing the Four Gospels, a fragment of Hebrew names, and the Eusebian canons, known also as the "Book of Columba", probably because it was written in the monastery of Iona to honour the saint. It is likely that it is to this book that the entry in the "Annals of Ulster" under the year 1006 refers, recording that in that year the "Gospel of Columba" was stolen. According to tradition, the book is a relic from the time of Columba (d. 597) and even the work of his hands, but, on palæographic grounds and judging by the character of the ornamentation, this tradition cannot be sustained, and the date of the composition of the book can hardly be placed earlier than the end of the seventh or beginning of the eighth century. This must be the book which the Welshman, Geraldus Cambrensis, saw at Kildare in the last quarter of the twelfth century and which he describes in glowing terms (Topogr. Hibern., II, xxxviii). We next hear of it at the cathedral of Kells (Irish Cenannus) in Meath, a foundation of Columba's, where it remained for a long time, or until the year 1541. In the seventeenth century Archbishop Ussher presented it to Trinity College, Dublin, where it is the most precious manuscript (A. I. 6) in the college library and by far the choicest relic of Irish art that has been preserved. In it is to be found every variety of design typical of Irish art at its best."
http://www.newadvent.org/cathen/08614b.htm