blue moon vs moment

blue moon

noun
  • A long time. 

  • The third full moon in a season that contains four rather than the usual three full moons. 

  • The second of two full moons that occur in the same calendar month (a definition created by mistake in the 20th century). 

  • A bright blue, sweet-flavored ice cream that is popular in the Midwestern U.S. and is a component of Superman ice cream. 

  • The moon tinted towards blue as it appears in the sky, caused by dust or smoke in the atmosphere. 

moment

noun
  • A brief, unspecified amount of time. 

  • Weight or importance. 

  • A fit; a brief tantrum. 

  • The smallest portion of time; an instant. 

  • A quantitative measure of the shape of a set of points. 

  • A petit mal episode; such a spell. 

  • (As in "X moment") An embarrassing event, supposed to be characteristic of some person, group, or situation. 

  • An infinitesimal change in a varying quantity; an increment or decrement. 

  • A definite period of time, specifically one-tenth of a point, or one-fortieth or one-fiftieth of an hour. 

How often have the words blue moon and moment occurred in a corpus of books? (source: Google Ngram Viewer )