Off the West coast of Ireland near the mouth of Galaway Bay there's a group of three islands called the Arans. Since the mid 19th century and earlier, a particularly heavy, incredibly warm, fisherman's sweater called the Aran has been produced here.
Traditionally, the wool used was not heavily scoured or treated and therefore retains much of the natural oil/grease which acts as a water repellant, essential for fishermen on the wild North Atlantic and Irish Sea. Derived from the Irish Gaelic bán or white, báinín is the term used to described the undyed wool used and is completely water repellant.
Photo Courtesy of: Clanarans
Thanks to personalities like Steve McQueen starring in the 'Thomas Crowne Affair' and the availability of commercially available patterns, the sweater gained widespread popularity in the 1950s and 60s.
Photo Courtesy of: United Artists
Historically, the sweater and numerous patterns have been part of the traditional garb of the the Aran islands and Ireland itself. Most noteworthy is that the patterns are used to represent the various Irish clans of which there are in excess of 100.
Additionally, the traditional local knitters were known to knit without any reference to a pattern and typically took 40 - 50 hours to produce each sweater.
So famous is the Aran that it has become a term for a weight of yarn, typically used in the British Isles and of course Ireland. It equates to a worsted or medium weight yarn using a USA 7-9 needle or USA 1-9 hook for crochet.
There's not many knitters on the islands these days, nor sheep apparently, but the sweaters are still made there using more modern methods and of course Merino wool. The closest Baah Yarn color would be La Perla from the Shasta collection (worsted weight).
If you would like to learn more and see what some Aran sweaters look like, here's a few links: