It's possible that tassels used to be reserved for chiefs, as with beret feathers. Bavaria used to be Celtic, and Hallstatt Celts in Austria had plaid in the Bronze Age, and used by Tocharian people of Russian steppes who had berets. The "gamsbart" tassel on national costume in Bavaria is made of "gamse/ gemse" chamois hair from a freshly-killed goat, which suggests ancient ritual. Zamaronnes in Galicia Spain wear zamara "fleece jacket" and a goat-head on their head, which would be pre-Christian.
As the military form of plaid was permitted by English, possibly the "royal service" type of sporran was the one which survived with kilts?