The Spanish word 'perno' meaning 'bolt' or 'pin' has an interesting evolution from Latin body parts to mechanical fasteners. It comes from the Latin word 'perna' meaning 'leg' or 'thigh'. This evolved into Vulgar Latin 'pernus' meaning 'support' or 'axis', showing how the meaning shifted from a body part to something that provides support. The word then entered Catalan as 'pern' before making its way into Spanish as 'perno', maintaining its meaning of a bolt or pin that provides support or acts as an axis point.

While 'perno' itself is a relatively basic mechanical term in Spanish, there aren't many simpler or more common Spanish words that share its exact etymology. However, Spanish students might find it helpful to think of a 'perno' as something that acts like a mechanical 'leg' or support for joining parts together, reflecting its original Latin meaning.

While English doesn't have many common words directly related to 'perno', there is an obscure English word 'pernio' (meaning chilblains) that comes from the same Latin root 'perna'. The word 'pernil' (meaning ham or leg of pork) is also related, though it's more commonly used in Spanish than English. These connections show how the original Latin word for 'leg' branched into different meanings across languages.