I know quite a few of my cousins (1C, 1C1R, 2C, 2C1R). Unless somebody asks me for the exact relationship, I tend to call them all cousins. Since not many people know the system for the rules of consanguinity, I usually describe somebody by a circumlocution like my father's cousin's son or some such. (There's a Danish branch to my family, and their terms depend on whether the cousin is female or male: kusine, fætter.)

Kinship terms are much studied in anthropology and linguistics. The interesting thing about IE kinship terms is that we cannot reconstruct a term for the proto-language (PIE) for cousin. All the daughter languages take a different approach.

I also looked into Irish col 'taboo, prohibition' which is interesting in its own right. Not an agreed upon etymology for the word. Vendryes suggests in his Old Irish etymological dictionary that it may be congate with Old Norse skyldr 'necessary, bounden'. There's also no reconstructed root for 'taboo' in PIE (which makes sense), though Cal Watkins has put one forward in the Umbrian sopa from the Iguvine Tables. A really cool thread, Hib, thanks for starting it.