means The quality of being morally upright — acting in accordance with what is considered just, virtuous, or in line with divine or ethical law.

from From Old English 'rihtwīs,' a marriage of 'riht' (right, just, straight) and 'wīs' (wise, the way of being — the same 'wise' tucked inside 'likewise' and 'clockwise'). So a 'rihtwīs' person was literally one wise in the right way, righteous-of-manner. Over centuries the spelling drifted and folk-tongues reshaped '-wise' into '-eous,' as if it had always been kin to words like 'courteous' — but the bones are pure Germanic 'right' plus 'way.' The abstract '-ness' was then bolted on to name the whole upright condition.