Green’s Dictionary of Slang

1. a person who is prim, prudish, often also effeminate, esp. when old.

1956		Amer. Vanguard (N.Y.) 87: So go mind your own business, Miss Prissy Pants, or go join the Salvation Army or something.
1968		N.Y. Mag. 16 Sept. 6: The stakes are too high for prissy-pants.
1974		(con. 1940s) E. Thompson Tattoo (1977) 217: He could just see them when a bedbug or roach crept out to test their faith. Prisspants Sharon would flat scream.
1975		E. Torres Carlito’s Way 131: Ol’ prissy-pants, Scott, would have a pained look on his puss.
1987		T. Janowitz Amer. Dad 98: I don’t need to have Miss Prissy-pants sulking all the way home because I turned out. Or is it turned on?
1987		Chronicles (N.Y.) XI 6/3: These times when novelists may be divided into prisspants like Truman Capote and foulmouths like Norman Mailer.
2005		A. Baxter Send and Receive 101: Better clean it up, [...] or Miss Prissy Pants will be on your case. She’ll probably leave a bucket and a cloth outside your door.

2. attrib. use of sense 1.

1934		New Leader (London) 5 Jan. 12/3: He is made a kind of prissy-pants writer, talking about his art and the fires burning inside of him.
1965		E. Hamner Jr You Can’t Get There from Here 175: But you try getting down in the middle of prissy-pants Park Avenue and barking at a dog and scratching his stomach and see where it gets you.