'censoriousness' originates from Latin, specifically the word 'censor', where 'censor' referred to a Roman official who assessed and judged citizens (the root sense being 'to assess or judge').

'censor' passed into Late Latin as 'censorius' and into Middle English as 'censor' and the adjective 'censorious' was formed in modern English; the noun 'censoriousness' was later formed by adding the suffix '-ness' to 'censorious'.

Initially related to the act of judging or assessing (as a censor's role), the sense shifted to emphasize harsh judgment of people's behavior or faults and came to mean 'inclination to criticize severely'.