1
general::
A phrase used to express disbelief, rejection, or self-deprecation. For example, They said we'd get an extra bonus at Christmas?? famous last words! or This book is bound to make the best-seller listfamous last words! This expression alludes to grandiose statements about human affairs that prove to be untrue, such as "This is the war to end all wars," or "We must make the world safe for democracy." [Late 1930s]
American Heritage Idioms
2
general::
Phrase(s): famous last words
Fig. assertions that are almost immediately countered. (Sarcastic.) • A: I said I would never speak to her again in my entire life! B: Famous last words! You just said hello to her.
McGrawhill's American Idioms And Phrasal Verbs