'av' (as abbreviation of 'audio-visual') originates from the modern English compound 'audio-visual', itself built from Latin-derived 'audio' (from Latin 'audire' meaning 'to hear') and 'visual' (from Latin 'videre' via French 'visual/visuel' meaning 'to see'). 'av' (as abbreviation of 'avenue') originates from French 'avenue', where the verb 'avenir' originally meant 'to come to/approach'.

'Audio-visual' is a 20th-century English compound formed to describe media combining sound and image; the initialism 'AV' arose in the 20th century to label related equipment and departments. 'Avenue' entered English from Old French (avenue) and Middle English; the postal/street abbreviation 'av.' developed later as addressing conventions standardized.

For the audio-visual sense, the original roots referenced 'hearing' and 'seeing', and the compound came to mean combined sound-and-image media; the abbreviation 'av' compresses that compound into an initialism. For the avenue sense, the original idea of 'coming toward' evolved into a noun for a way or approach and then into a street name; 'av.' became a postal/street abbreviation.