cretin

Concise Oxford English Dictionary © 2008 Oxford University Press:
cretin /ˈkrɛtɪn/

▶noun

• 1 a stupid person.

• 2 Medicine, dated a person who is physically deformed and has learning difficulties because of congenital thyroid deficiency.

– derivatives
cretinism noun,
cretinous adjective.

– origin C18: from Fr. crétin, from Swiss Fr. crestin ‘Christian’, appar. used to convey a reminder that such people are human.