Quickly; a "Shetland sweater" is one made of wool from a Shetland sheep, not one made in the Shetland Isles (100 miles north of the coast of Scotland) though the notoriously hardy sheep did supposedly originate there. Their yard may be ultra-fine (from the neck area) or more coarse, but the (often saddle-shouldered) crewneck sweater is generally from the rougher yarn. The sheep themselves have a wide range of colors and markings from coal black to brown to pure white but the white sheep are morepopular as the wool can then be dyed.
So what? So, these sweaters are hard wearing due to the rougher wool, generally inexpensive (in Scotland), hold their shape better than cotton, and thus have became a preppy staple. Top photo taken yday, below in 1989 (not same sweater but I guess my taste hasn't changed) just home from high school Christmas service (evidenced by kilt), cranking Galiga sound effects on the headphones. #geekery
