The Spanish word 'rodilla' meaning 'knee' has an interesting etymological journey that starts with the Latin word 'rota' meaning 'wheel'. This evolved into the Late Latin diminutive form 'rotella', meaning 'small wheel'. The transformation from 'small wheel' to 'knee' in Spanish makes intuitive sense when you consider the knee's round shape and its rotating motion, similar to a small wheel. The phonetic evolution from 'rotella' to 'rodilla' followed regular sound changes in Spanish, where the 't' became voiced to 'd' between vowels, and the '-ella' ending evolved into the Spanish '-illa'.

Several common Spanish words share this wheeled ancestry with 'rodilla'. The word 'rueda' (wheel) comes directly from Latin 'rota', and 'rodar' (to roll) is also related. You can see how all these words share the concept of circular motion or round shapes.

English speakers might recognize this connection in words like 'rotate', 'rotary', and 'rotunda', all of which come from the same Latin root 'rota'. Even the word 'round' is distantly related. This common etymology emphasizes the connection between circular motion and the function of the knee as a pivotal joint in the body.