'audio' (as a modern English noun/adjective) originates from New Latin/Modern English usage, ultimately from the Latin verb 'audīre' (to hear); the form 'audio' is Latin first-person singular present meaning 'I hear', which gave the combining form 'audio-' and later the standalone word 'audio'.

The element comes from Latin 'audīre' → Latin form 'audio' ('I hear') → used in New Latin and scientific/technical coinages as the combining form 'audio-' in the late 19th–early 20th century, and then shortened in English to the noun/adjective 'audio' (20th century) meaning 'sound' or 'relating to sound'.

Initially in Latin it literally meant 'I hear', but over time the term became a root/combining form meaning 'relating to hearing or sound' and then further evolved into the English noun/adjective meaning 'sound' or 'relating to sound/reproduction of sound'.