My Family are from Scotland but my name isn’t a clan name – how is this possible?

Coats of Arms
Is there a family coat of arms

Clan Crests
Who can wear a clan crest?

The rule of eagle feathers in your cap, what do they mean?
Chief: 3 Feathers behind the Crest. Chieftain: 2 Feathers, and lastly, Armigerous Gentleman (Armiger): a single eagles feather behind the Crest.