folklore
in the 1950's and '60's it was common to believe that a small gremlin or troll would sneak into the dryer when you weren't looking, and steal your socks. gremlins and trolls would never collect pairs, only mismatched socks. this relatively modern folklore was the inspiration for the "underpants gnomes" on a south park episode. unfortunately, no-one has ever found a gremlin or troll lair, so no-one knows exactly what they do with all the socks they have collected. do they make clothes from them? sell them on e-bay? trade them with other gremlins or trolls, maybe this is there form of currency?