'priggish' originates from English, specifically from the base word 'prig' plus the suffix '-ish', where 'prig' meant 'a conceitedly proper or self-righteous person' and '-ish' meant 'having the quality of'.

'prig' appeared in early 17th-century English with senses that included a conceited, self-righteous person (and in some dialectal uses earlier senses like 'to steal' are attested); the adjective 'priggish' developed by adding the adjectival suffix '-ish' to describe someone having the qualities of a 'prig'.

Initially it referred to a person described as a 'prig' (conceited about propriety); over time the adjective 'priggish' has come to mean generally 'self-righteously proper' or 'excessively prim'.