Machine, AI, being, God? The best guarded secret of the country of Egypt, Former Earth. One which secured them their galactic future and survival, at the same time, damning them in the eyes of every nation of the Republic for an eternity.
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.