flathead · noun1
Flathead · noun, proper noun2
From flat + head, from the practice of compressing the skull in infancy by artificial means. However, the Salish tribe never practised this custom, the confusion arising from the fact that the early traders felt compelled to adopt the local Indian classification, which considered the prevailing compressed skull of the neighbouring tribes as pointed and the naturally shaped Salish skull by contrast as flat.
Etymology from Wiktionary, CC BY-SA 4.0.