Righteousness
Old English rihtwīs, from riht ‘right’ + wīs ‘manner, state, condition’. The change in the ending in the 16th century was due to association with words such as bounteous .
wiktionary
From Middle English rightwisnes, from Old English rihtwīsnes(“justice”).
etymonline
righteousness (n.)
"character of being righteous; purity of heart and rectitude of life; the being and doing right; conformity in character and conduct to a right standard;" an alteration, attested by early 15c., of Middle English rightwisnesse "rightwise," from Old English rehtwisnisse "justice, conformity to divine or moral law;" see righteous + -ness. The original form is now obscure or archaic. Tyndale (1526) has "Blessed are they which honger and thurst for rightewesnes" where KJV has "Blessed are they which do hunger and thirst after righteousness" [Matthew v.6].
