The Spanish word 'lado' meaning 'side' comes directly from the Latin word 'latus', which also meant 'side'. This is a straightforward inheritance where the Latin 't' changed to 'd' in Spanish, a common sound change between these languages, while maintaining the same meaning.

Some related Spanish words include 'lateral' (lateral/side), which is a more formal term derived from the same Latin root 'latus'. Another common phrase is 'al lado de' meaning 'next to' or 'beside', which literally means 'to the side of'.

Several English words are related to 'lado' through the shared Latin ancestor 'latus'. These include 'lateral' (relating to the side), 'latitude' (originally measuring width from side to side), and 'collateral' (meaning 'side by side' or 'parallel'). The scientific term 'bilateral' (having two sides) also contains this root.