'arvos' originates from Australian English, specifically the clipped form 'arvo' of the word 'afternoon', where 'after' meant 'later' and 'noon' meant 'midday'.

'arvo' developed as a colloquial shortening of 'afternoon' in Australian English; the plural form 'arvos' follows standard English pluralization.

Initially 'afternoon' literally meant 'after noon'; over time the clipped form 'arvo' (and 'arvos') came to be used informally to mean 'afternoon(s)'.