'unpraiseworthy' originates from English, specifically formed from the negative prefix 'un-' and the word 'praiseworthy', where 'un-' meant 'not' and 'praiseworthy' meant 'deserving praise'.

'praiseworthy' comes from 'praise' + 'worthy'. 'Praise' developed from Middle English 'preisen' (from Old French 'preisier'/'preiser'), ultimately from Late Latin 'pretiāre' (related to Latin 'pretium' meaning 'price, value'); 'worthy' comes from Old English 'weorþe' meaning 'of value or worthy'. The modern adjective 'unpraiseworthy' was formed in English by prefixing 'un-' to 'praiseworthy'.

Initially built to mean 'not deserving praise' (the literal negative of 'praiseworthy'), the meaning has remained essentially the same and is used to indicate actions or behavior that merit blame or criticism rather than praise.