1
general::
Disparaging what one cannot obtain, as in The losers' scorn for the award is pure sour grapes. This expression alludes to the Greek writer Aesop's famous fable about a fox that cannot reach some grapes on a high vine and announces that they are sour. In English the fable was first recorded in William Caxton's 1484 translation, "The fox said these raisins be sour."
American Heritage Idioms
2
general::
Phrase(s): sour grapes
Fig. something that one cannot have and so disparages as if it were never desirable. • Of course you want to buy this expensive jacket. Criticizing it is just sour grapes, but you still really want it.
McGrawhill's American Idioms And Phrasal Verbs