Most often used mockingly or sarcastically: an obviously innocent and virtuous young woman

I was dumbfounded when I heard that Miss Goody two-shoes, who never puts a finger wrong, was having an affair with a married man

Sono rimasta senza parole quando ho saputo che quella madonnina infilzata se la faceva con un uomo sposato

From the name of the heroine of a child's story, written probably by Oliver Goldsmith (18th century). The little girl was so poor that she owned only one shoe. When she received a second one, she was so happy that went around showing both of them to everybody, cheering "Two shoes!"