The Spanish word 'pie' meaning 'foot' comes from the Latin word 'pes' (in its accusative form 'pedem'). This Latin root underwent sound changes as it evolved into Spanish, with the 'd' being lost and the vowel shifting to 'ie'.

This evolution from Latin to Spanish follows a common pattern where Latin words often underwent significant phonetic changes while maintaining their core meaning related to body parts.

Several common Spanish words are derived from the same Latin root, including 'peatón' (pedestrian), 'pedal' (pedal), and 'pedestal' (pedestal). All these words maintain a connection to the basic concept of 'foot' or 'walking'.

English speakers can easily remember 'pie' by connecting it to several English words that come from the same Latin root 'pes/pedem'. These include 'pedestrian' (someone who goes on foot), 'pedal' (operated by foot), 'pedestal' (foot of a column), and even 'pedigree' (literally 'crane's foot', from the appearance of genealogical trees). The word 'pawn' in chess also comes from this root, originally meaning 'one who goes on foot'.