The Foreign Secretary warned in a newspaper article that voters should not be lulled into thinking that Mr Corbyn was a "mutton-headed old mugwump" who was essentially harmless.
Johnson: May is leader UK needs in “age of uncertainty”And he revealed that he believed the obscure term referred to a character in a children's classic by Roald Dahl.
"It's a long time since I read it, but I think it's in Charlie And The Chocolate Factory," Mr Johnson told ITV1's Good Morning Britain.
"I think Willy Wonka says it either to the parents of Violet Beauregarde or Augustus Gloop."
In fact, mugwump is a native American term for a war leader, which was taken up in the 1880s to describe members of the US Republican party who switched parties to support Democrat presidential candidate Grover Cleveland. For some time afterwards, the word was used in the US to describe a political turncoat.
More recently, mugwumps featured in the graphic and surrealistic novel Naked Lunch by Beat Generation writer William Burroughs - filmed by David Cronenberg in 1991 - as a bizarre and reptilian alien species.
The term also appeared in the best-selling Harry Potter series, to describe members of the International Confederation of Wizards - of which the character Albus Dumbledore was appointed the Supreme Mugwump.
Mugwumps even entered the UK pop charts in 1994, when they were mentioned in the chorus of Bomb The Bass hit Bug Powder Dust, a homage to the Burroughs book.
Muggle-Wump the Monkey appeared in Dahl's story The Twits.