a sweet-smelling liquid ester, C7H14O2, a mixture of isomers derived from amyl alcohol and having the characteristic odor of bananas: used chiefly as a paint solvent and in artificial fruit flavors; amyl acetate.
Nonsense, exaggerated flattery, as in I should be on television? Cut out the banana oil! The precise analogy in this idiom is not clear, unless it is to the fact that banana oil, a paint solvent and artificial flavoring agent, has no relation to the fruit other than that it smells like it. Possibly it is a variation on snake oil, a term for quack medicine that was extended to mean nonsense. [1920s]