A goody two-shoes is a prudish or morally upright person. It’s an odd term to the modern ear. What do shoes have to do with being good?
The term comes from the title character in the 1765 The History of Little Goody Two-Shoes:
The Pleasure she took in her two Shoes...by that Means obtained the Name of Goody Two-Shoes.1
The goody in the name has nothing to do with being good. Rather, it’s an abbreviated form of goodwife, the mistress of a house, the equivalent of the modern Mrs. Later readers, unfamiliar with that form of address, took it to mean pious or virtuous.
The slang usage is 20th century. From the Los Angeles Times, 30 May 1924, in a description of a boxing match:
The two showed much brotherly affection in the first and second round thereby bringing a Kansas tornado of yips and catcalls from the angered fans. Hollywood bugs brook no Goody-Two-Shoes bouts.2
2”Callahan Defeated by Adams,” Los Angeles Times (Los Angeles), 30 May 1924, 9.
Copyright 1997-2015, by David Wilton