prig /prɪɡ/ BrE AmE noun [countable]
[ Date: 1600-1700 ; Origin: Probably from prig 'showy man' (17-19 centuries) , perhaps from prig 'tinker, thief' (16-19 centuries) ]
someone who behaves in a morally good way and shows that they disapprove of the way other people behave – used to show disapproval:
Don’t be such a prig! It’s only a bit of harmless fun!
—priggish adjective :
a rather priggish, old-fashioned man
—priggishness noun [uncountable]