'centerline' originates from the combination of 'center' and 'line', where 'center' meant 'middle point' and 'line' referred to a 'straight path'.

'centerline' evolved from the Middle English word 'centre' and the Old English word 'line', eventually becoming the modern English word 'centerline'.

Initially, it meant 'a line through the center', and this meaning has largely remained the same in modern usage.