Green’s Dictionary of Slang

priggish, puritan, ‘goody-goody’.

1909		J. Ware Passing Eng. of the Victorian Era.
1934		T. Minehan Boy and Girl Tramps of America (1976) 141: ‘You big fat fool,’ she called him, ‘you Y.M.C.A. dummy. Why did you have to spoil it all?’.