1
general::
Pass off by deception, substitute with intent to deceive, as in The salesman tried to palm off a zircon as a diamond, or The producer tried to palm her off as a star from the Metropolitan Opera. This expression alludes to concealing something in the palm of one's hand. It replaced the earlier palm on in the early 1800s.
American Heritage Idioms
2
general::
Phrase(s): palm someone or something off (on someone) (as someone or something) [and] pass someone or something off (on someone) (as someone or something); pawn someone or something off (on someone) (as someone or something)
Fig. to give someone or something to someone as a gift that appears to be someone or something desirable. (As if the gift had been concealed in one’s palm until it was gotten rid of.) • Are you trying to palm that annoying client off on me as a hot prospect? • Don’t palm off that pest on me. • Please don’t pass that problem off on me as a challenge. • Don’t pass it off on me! • Don’t pawn it off on me as something of value.
McGrawhill's American Idioms And Phrasal Verbs