The Spanish verb 'asegurar' (meaning 'to secure' or 'to ensure') comes from the Latin word 'securus', which meant 'free from care' or 'safe'. The Latin 'securus' itself was formed from two parts: the prefix 'se-' meaning 'apart' and 'cura' meaning 'care or concern' - so literally meaning 'without care' or 'free from worry'. In Spanish, 'securus' evolved into the adjective 'seguro' ('safe, secure'), and then the verb 'asegurar' was formed by adding the prefix 'a-' (meaning 'toward') and the verb suffix '-ar'.

The most common related Spanish word is the adjective 'seguro', meaning 'safe' or 'secure'. You might hear this in common phrases like '¿estás seguro?' (are you sure?) or 'seguridad' (security). These all share the core meaning of safety and certainty from the Latin 'securus'.

English speakers will recognize this connection in words like 'secure', 'sure', and 'assure', which all come from the same Latin root 'securus'. Just as 'asegurar' means 'to make secure or certain', the English word 'assure' (which has the same prefix 'a-') means 'to make sure or certain'. The connection between 'seguro' and 'sure' becomes quite clear when you consider their shared origin and meaning!