'separately-sectioned' originates from the combination of 'separate' and 'section,' where 'separate' meant 'to set apart' and 'section' meant 'a distinct part or division.'

'separate' and 'section' were combined in modern English to form the compound adjective 'separately-sectioned.'

Initially, 'separate' and 'section' were used independently, but over time they evolved into the compound form to describe something divided into distinct parts.