What is a mugwump and why did Boris Johnson say Jeremy Corbyn is mutton-headed?

FOREIGN secretary Boris Johnson called Labour leader Jeremy Corbyn a "mutton-headed old mugwump" and claimed he would be a threat to national security if elected Prime Minister.

But what is a mugwump, and why is the former Mayor of London using it to describe Corbyn?

What is a mugwump?

In an article for the Sun, Mr Johnson said: "They watch his meandering and nonsensical questions and they feel a terrible twinge of human compassion.

"Well, they say to themselves: he may be a mutton-headed old mugwump, but he is probably harmless."

The term mugwump was used to describe the Republican Party political activists who refused to support their own candidate, James G. Baine,  in the US presidential election of 1884.

The word derives from an Algonquin Native American word mugquomp, which means an important person. James G. Baine was mired in political scandal, and the word was used to imply that by refusing to support him the mugwumps were sanctimonious.

What does mutton-headed mean?

According to Collins Dictionary, a muttonhead is "a stupid or ignorant person". The reference to mutton is because of the belief that sheep are stupid.

What was the reaction?

Shadow cabinet minister John Healey said he had to look up the word "mugwump" and criticised Mr Johnson for attention-seeking.

He told BBC Radio 4's Today programme: "I think this is Boris Johnson feeling left out of the election campaign and it's the sort of look-at-me name calling that you would expect in an Eton playground.

"I simply don't want to sink to that sort of level to respond, I think it demeans the position of Britain's Foreign Secretary."