evening dress vs frock

evening dress

noun
  • An elegant dress worn by women, especially for social events in the evening, an evening gown. 

  • formal attire worn for evening social events. 

frock

noun
  • A dress, a piece of clothing, which consists of a skirt and a cover for the upper body. 

  • An outer garment worn by priests and other clericals; a habit. 

  • A sailor's jersey. 

  • An undress regimental coat. 

  • A frog. 

verb
  • To make (somebody) a cleric. 

  • To clothe (somebody) in a frock. 

  • To grant to an officer the title and uniform of a rank he will soon be promoted to. 

How often have the words evening dress and frock occurred in a corpus of books? (source: Google Ngram Viewer )