noun, feminine/pu.dʁə d(ə) pɛʁ.lɛ̃.pɛ̃.pɛ̃/plural: poudres de perlimpinpin
a powder, purported to have magic powers, formerly sold by charlatans; snake oil (a fraudulent cure-all or remedy)
“2017, Emmanuel Macron, 2017, le débat, TF1/France 2” — So what you have to offer, as usual, is nothing but snake oil.
Attested since the 17th century, originally as poudre de prelimpinpin. Compare Portuguese pó de perlimpimpim.