The Spanish word 'anfibio' comes from Latin 'amphibius', which was borrowed from Ancient Greek 'amphibios' (ἀμφίβιος), meaning 'living in two elements'. The Greek word was formed by combining two elements: 'amphi-' (ἀμφί) meaning 'on both sides' and 'bios' (βίος) meaning 'life'. This perfectly describes amphibians, as they live both in water and on land. The change from 'amphi-' to 'anfi-' in Spanish reflects a common sound change pattern in Spanish where 'mph' becomes 'nf'.

The prefix 'anfi-' appears in other Spanish words like 'anfiteatro' (amphitheater), which describes a theater with seats on both sides, and 'anfitrión' (host), though these might not be simpler for beginners. The element 'bio' appears in many common Spanish words like 'biología' (biology), 'biografía' (biography), and 'biológico' (biological), all relating to life or living things.

English speakers can easily connect 'anfibio' to the English word 'amphibian', which shares the exact same Greek origin and meaning. Other related English words include 'amphibious' (able to operate both on land and in water) and words using the same root elements like 'amphitheater' (from 'amphi-' meaning 'both sides') and 'biology', 'biography', 'biosphere' (from 'bio-' meaning 'life').