My clue here was the placename “Kyles”, meaning “straits” or “narrows”. The Kyles of Ra, the Kyles of Bute, and Kyleakin on the Isle of Skye are all Anglicizations of “caolas”, strait or narrows. The word derives, logically enough, from “caol”, narrow, slender, slim, thin. And for various reasons, your conveniently differentiated “ao” in Scottish Gaelic or modern Irish is usually spelled “ae” in early Irish. So “caol” is exactly the same word as “cael” — just a little different pronunciation.*
For the period between the Middle Ages and the last fifty years or so, Kyle was best known as the name of a small Scottish family mostly found in North Lanarkshire, who apparently originally hailed from a small Scottish barony in Ayrshire, a bit further west. Kyle was a property of the Stuarts, so presently its lairdship is held by the Prince of Wales. Kyle was apparently named for the River Kyle, which is indeed a narrow one. However, tradition also indicates a link to Coel Hen (Coel the Old, probably the source of the Old King Cole legend), one of the old Welsh kings of Northern England and southern bits of Scotland. Coel was the father of St. Ceneu (or Kenneth) ap Coel. (Like many Welsh king saints, he seems to be regarded as a saints for his defense of his country against pagan enemies, like the Saxon and Irish pirates.) Coel is said to have died in Coilsfield, Tarbolton, Ayrshire, and been buried in the church at Coylton about AD 420.
But Caol or Cael by itself was a pretty common unisex name in early Ireland. There was a St. Cael who was one of the four daughters of Mac Iaar whose feast was celebrated on October 26. St. Caol the Devout (Coelius in Latin, thus a guy) was listed in one of the martyrologies, and there was St. Caila or Caelius on Nov. 10.
Caol and Cael were also extremely common bynames for Irish and Scottish people. (A byname or nickname is how you distinguish one Sean from another. Sean Cael would be Thin Sean, Sean Mor is Big Sean, Sean Beg is Little Sean, Sean Dubh is Darkhaired Sean, etc.)
So it’s not surprising that saints have this byname. St. Conall Caol was a monk. He lived in Donegal on Inishkeel (Inis Chaol – Thin Island) which was apparently named after him, though it might just be a bad pun. One of his friends was St. Dallan Forgaill, the poet turned monk who composed “Amra Choluim Cille”. Through a twist of fate that made Dallan’s long-expressed wish come true, the two were buried in one grave. St. Conall Caol was also connected in legend with the Sunday Law, which he was supposed to have fetched from Rome. We don’t know why this legendary connection is made, since he apparently had nothing historically to do with the Sunday Law’s appearance, but maybe he promoted it. The British Museum has St. Conall Caol’s Bell, which once resided at his shrine. However, the “turas” or “station” pilgrimages still go on today on Inishkeel.
(There’s also St. Cruimther Caol, a guy apparently associated with St. Enda. His feast is May 25.)
However, there are also given names derived from “cael”. I don’t know any saints named “Cailte” or “Caolfhionn”. There’s a female St. Caellain or Caeilfhionn from Kilkeevin, who was the patron saint of the Ciarraidhe of Connaught. However, there are at least two male saints named “thin one” — St. Caelan, of Iniscealtra on the Shannon, and St. Caolan***, of County Down. St. Caolan lived in the early part of the sixth century. (He may have been born late in the 5th century, like his brother, St. Donard.) His brother was one of St. Patrick’s disciples. St. Caelan was a monk who lived in the first half of the eighth century. He is known to us as the composer of a life of St. Brigid in Latin hexameters. His feast was July 29.
Other Caelans included: St. Caelan of Cilleo, June 30; St. Caelan of Doire or Doire-Chaolain, June 19; St. Caelan of Echinis, Sept. 25; and St. Caelan of Tigh-na-manach, Oct. 29.**
So I think you Kyles out there are totally covered on the saint’s name front.
“Kylie” is a more difficult name, as Kylie Minogue was notoriously given an Australian aboriginal name. (Possibly meaning “boomerang”.) However, if you wish to interpret Kylie as a diminutive of Kyle, you also have all the Caels and Caelans to choose from.
* The problem with an old language is that the sounds of it can be very different, depending on where it’s being spoken. Take the name “Sean”, for example. Originally, both vowels would have gotten full value, and it would have been pronounced something like “shay-on”. In the south and west of Ireland today, they ignore the “e” sound and just say “shawn”. In the north and east of Ireland, or in Scotland, the “a” gets ignored instead and it’s pronounced “shane”.
Not surprisingly, the same thing happened with cael/caol. The usual Irish pronunciation is apparently “keel” or “kweel”. The usual Scottish pronunciation is… um… well, you can try saying “cool” in a much tighter way. Or you can say a short “a” as in the American pronunciation of “cat”, and add an “o”… or…
Well, you can understand how that kind of weird sound got anglicized to Kyle.
** The vast majority of these guys (and gals) were located by searching books.google.com and finding Cyclopedia of Biblical, Theological, and Ecclesiastical Literature by John McClintock. The Martyrology of Donegal by Michael O’Clery also includes them, with some more info.
*** “caolan” apparently can also mean “the small intestine”, because the gut was supposed to be “the narrowest thing in the body” according to the Yellow Book of Lecan. (So says The Games and Diversions of Argyleshire, by Robert Craig Maclagan.)