If one travels, you might notice it. Each one has a blue orb on their signage or somewhere in the shop. The merchants seem to specialize in foreign goods, but often buy local produce and products, to trade in other places. They seem totally unrelated to the others. It seems to be a secret organization, but nobody knows for sure.
The size and number of knots in hair, tied around neck, or hanging from belt could signify family, importance, worship, guild affiliations. Being able to translate the meaning of the size and placement of knots can give you a a large understanding of who somebody is.
May be used in a more barbaric society. Where in cities peoples clothes and crests show who they are, barbarians have no need for this so use knots.