JFTR, in the name “Cathal”, the “t” is silent, so it’s pronounced “Cahal” (also the letter “a” has the short-vowel sound). Alternate transliteration is “Cahill”.
Crannogs (though not called by that name) feature in one of my favorite pieces of fiction, Gene Wolfe’s Solar Cycle. In one of the books, the hero encounters a society where half of the population lives on crannogs in a lake and half lives on the shore. The shore people kidnap and enslave the island people, and the island people retaliate by attacking the shore people when they go out on their fishing boats.
Is this one of those “round” boats?