'high-altitude' originates from the combination of 'high' and 'altitude', where 'high' means 'great in vertical extent' and 'altitude' refers to 'height above sea level'.

'High-altitude' combines the Old English word 'hēah' (high) and the Latin word 'altitudo' (altitude), eventually forming the modern English term 'high-altitude'.

Initially, it referred to any great height, but over time it evolved to specifically denote significant heights above sea level.