Back before cretin meant “a stupid person,” it was a medical term for a physical deformity that came from a specific disease. Surprisingly, the root of cretin is the Swiss French word crestin, which means “Christian.” It seems that people back then wanted to remind themselves that even though cretins look unusual, they’re still humans who deserve kindness. Knowing this makes it hard to use cretin in a mean way, but there are plenty more rude words you could use.