Prim means stiffly correct and easily shocked. A prim manner, prim and proper, sat there prim.
It is faintly mocking and it is used of women far more than of men, which dates it. Prim and proper is the fixed phrase. The word describes an attitude to propriety rather than propriety itself — somebody prim is not virtuous so much as disapproving. Note that the origin of the word is uncertain.
1adjectiveprimStiffly correct and easily shocked.
“Her prim aunt was shocked when the comedian started swearing.”
synonyms: prudish, prissy
prim is a quality of stiff propriety.
The origin of prim is uncertain. It appears in English in the seventeenth century as a verb and a noun before an adjective.
Proto-Indo-European
*per-
English, today
prim
Of uncertain origin. In the verb sense, first appeared in Thomas D'Urfey's A Fool's Preferment in the year 1688. In the noun sense, first appeared in A New Dictionary of the Terms Ancient and Modern of the Canting Crew in the year 1699, meaning "prig." Now obsolete.
Etymology from Wiktionary, CC BY-SA