The Spanish word 'amigo' meaning 'friend' comes from the Latin word 'amicus', which also meant 'friend'. The Latin 'amicus' itself was formed by combining two parts: the verb 'amare' meaning 'to love' and the suffix '-icus' which was used to form adjectives and nouns related to the base word. So etymologically, an 'amigo' is literally someone who is 'related to love' or 'characterized by love'.

The evolution from Latin 'amicus' to Spanish 'amigo' shows a common sound change pattern in the development from Latin to Spanish, where the 'c' sound softened to a 'g'.

Several common Spanish words share the same Latin root 'amare' (to love). These include 'amor' (love), 'amar' (to love), 'amante' (lover), and 'amable' (friendly, kind). All these words preserve the core meaning related to love and affection, with 'amigo' specifically focusing on the friendship aspect of loving relationships.

The English word 'amiable', meaning friendly and pleasant, comes from the same Latin root as 'amigo'. Another related English word is 'amicable', meaning friendly or peaceful, which comes directly from Latin 'amicus'. The word 'amateur', though it might not seem obviously related, also comes from the Latin 'amare', as it originally referred to someone who does something for the love of it rather than professionally.