'air-filled' originates from the combination of 'air' and 'filled', where 'air' refers to the invisible gaseous substance surrounding the earth, and 'filled' means to make full.

'Air' comes from Old English 'ær', and 'filled' comes from Old English 'fyllan', meaning to fill.

Initially, 'air-filled' simply meant 'filled with air', and this meaning has remained consistent over time.