Image copyright AP

Donald Trump fans have been condemned for calling her one, while some of her supporters have urged her to be more of one. So why is Hillary Clinton so often associated with the word "bitch" - and how offensive is it?

Supporters of Donald Trump have sparked outrage in US media with merchandise attacking Hillary Clinton that many people say uses lewd and demeaning language.

T-shirts saying "Trump that bitch" and badges with similar mottos were found on display at rallies. Despite the media outrage, both men and women at a rally in West Virginia told the Washington Post they thought the items were "funny". They liked the way the shirts defied political correctness, something the presumptive Republican nominee has railed against.

The shirts are not authorised by Mr Trump's campaign. But a simple online search reveals a whole range of unofficial items such as bumper stickers displaying the same word in reference to the first female presidential candidate for a major party in the US.

Image copyright Caroline Modarressy-Tehrani Image caption Huffington Post journalist Caroline Modarressy-Tehrani photographed this T-shirt being sold outside a Trump event in Rhode Island

And is not just Mrs Clinton's detractors who use the term. Tina Brown, former editor of the New Yorker and Vanity Fair, told the BBC's Today programme that the Democratic nominee needed to "own her inner bitch" in order to appeal to young women voters.

Some experts argue the taboo around the word has changed. Of course, women can buy themselves T-shirts and necklaces labelling themselves "bitch".

But as anyone who has been called it by a passer-by in the street, or at work, will know - it can still pack a painful punch. Why is that?

Media playback is unsupported on your device Media caption Hillary Clinton 'must own her inner bitch' to win young voters says Tina Brown

The term "bitch" has been used to refer to a female dog since about 1000 AD, according to the Oxford English Dictionary, and began to be used as a pejorative term for women in around the 15th Century.

The 1811 edition of the Dictionary of the Vulgar Tongue by Francis Grose said it was "most offensive appellation that can be given to an English woman".

The OED defines its modern meaning as "a malicious or treacherous woman" or "something outstandingly difficult or unpleasant". But other dictionary definitions say its premier use is no longer as a term of abuse.

"It has gone through this whole history of the way words change," says Connie Eble, an English professor at the University of North Carolina who has documented the language of college students for some 40 years.

"There are some really interesting things going on it popular culture that are informing its usage."

Media playback is unsupported on your device Media caption How do women in Washington DC feel about using the word "bitch"?

While female students often affectionately refer to friends as "bitches", she says, the term "bitchin" is commonly used as a positive description by young people in the US. "Bitch" can also be used as a verb, meaning to "complain". Or changing it to "biatch" can add humour or force.

Behind much of the change has been American and British hip hop that used "bitch" simply to refer to a woman, says Eble. Music critics pointed out that Madonna used dozens of times on her latest album. But it also follows a campaign for women to reclaim the word.

A feminist magazine called Bitch was set up 1996. Its founders wanted to use the title to spark debate about language and talk about women's rights.

Andi Zeisler, a co-founder of the magazine, says the controversial title was inspired by the way the word "queer" had been appropriated by the LGBT community.

But she says it has been both "fascinating and frustrating" to see how attitudes to the word "bitch" has changed since.

What does "bitch" mean in slang?

A woman (noun)

A despicable woman (noun)

A feminine or weak man (noun)

A sexually submissive person (noun)

something that is difficult or unpleasant (noun)

to complain (verb)

to inform (verb)

Source: The Concise New Partridge Dictionary of Slang and Unconventional English

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"When we started the organisation, bitch wasn't used in common parlance the way it is now," says Zeisler. "It was still very much an epithet for a woman who was doing or saying something that other people did not want to hear."

But in the years that followed it became "very normalised to hear it as a synonym for a woman", she says. "People started to use it as a term of endearment or as emphasis."

However, the core meaning of the word has not changed, she says. "It's still the most common way to describe a woman who's doing something that people do not like."

So she was not surprised to see Trump supporters using the term.

"Hillary Clinton has been thought of as a bitch since she was first lady," Zeisler says. "That was not because she was seen as mean spirited or petty - but because she had ambitions that people thought were above her station."

Critics of Mrs Clinton have repeatedly pointed to her alleged mishandling of issues such as healthcare reform, and the scandal surrounding her husband's affair with Monica Lewinsky.

Image copyright Getty Images Image caption Supporters of Hillary Clinton say she has been the target of sexism for many years

More recently she has been lambasted over the fatal attack on a US compound in the Libyan city of Benghazi in 2012, and her use of private email for official business while she was secretary of state.

Nick Adams, a political commentator and author of the book Retaking America: Crushing Political Correctness, says the insult is justified.

"I would submit that Hillary Clinton is dishonest, malicious, spiteful, overbearing, difficult, objectionable and unpleasant. Given these characteristics, many would consider the term "bitch" fitting," he says.

He says people offended by the term are being "precious". "Politics is a merciless, competitive, blood sport," he says. "It is not new to have candidates and their supporters of all political stripes hurl epithets, coin pejoratives or invent insults."

Image copyright AP Image caption Donald Trump has not called Mrs Clinton a "bitch" but prefers the nickname Lying Crooked Hillary

Women's rights activists and some left-wing commentators particularly object to the way "bitch" refers to Mrs Clinton's gender, and say male politicians are not treated in the same way.

Meanwhile Tom Dalzell, a slang expert, believes the taboo around using it now is greater than ever before because there is more of an expectation that women will be treated fairly. Slurs that are specifically directed at certain groups of people are seen as unacceptable, he adds.

"It has come to show hatred in a way it didn't 30 years ago."

This does depend on who is using it and how. But he says the reclamation effort has only been partially successful.

Certainly Trump supporters are not using it out of affection or solidarity.

Andi Zeisler says its appearance at Trump rallies is particularly "offensive" because of the way the Republican nominee "whips up his fans in this kind of blood bath, in a specifically threatening and violent way".

But the rhetoric around the election will continue to build over the coming months.

And considering its long and complicated history, the "bitch" in the room is unlikely to go away any time soon.