A tautology is a statement that’s true by definition, often because it repeats the same idea in different words. In place names, tautological names redundantly combine words meaning the same thing in different languages.

Common examples:

• River Avon - “Avon” comes from Welsh meaning “river,” so this literally means “River River”
• Sahara Desert - “Sahara” means “desert” in Arabic, making this “Desert Desert”
• Mount Fujiyama - “Yama” means “mountain” in Japanese, so “Mount Fuji Mountain”
• Torpenhow Hill - Possibly the most extreme example, where each component (tor, pen, how) means “hill” in different Celtic and Old English languages

These arise when colonizers or map-makers encounter local place names and add their own word for the geographic feature, not realizing the name already includes that meaning.

In logic and programming, tautologies also appear as statements that are always true regardless of variables: if (x == x) or A OR NOT A. While logically valid, they’re often redundant or indicate unclear thinking.

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