'upper-floor' originates from the combination of 'upper,' meaning 'higher,' and 'floor,' referring to a level of a building.

'Upper' and 'floor' have been used in English since the Middle Ages, with 'upper' deriving from Old English 'uferra' and 'floor' from Old English 'flōr.'

Initially, 'upper-floor' simply referred to any floor above the ground level, and this meaning has remained consistent.