To my knowledge, there wasn't a famous
Caitlin who made the name prominent: variants of
Katharine take turns in surfacing from time to time, like all the Kathys in the 1950s whose daughters are Kates; and then there's
Kathryn and
Kathleen, and the very dated
Kitty as a nickname. And
Caitlin was just a
Katharine version whose time had come; plus, as CKE says, in Wales and
Ireland it doesn't sound like
Kate +
Lyn so people probably saw it, liked what they thought it sounded like, and so its use snowballed.
The fact that your parents liked the 'sound' of the name but can't trace it back to a single source probably confirms this. Anyway, lucky you: most Caitlins are younger than you, so if you ever want to shed a few years or a decade or two, your name will make it easy!