"Fake news" has rarely been out of the news since Donald Trumps unlikely election to the White House.

Rarely a day goes by when the president doesn't take to Twitter to accuse, normally in capital letters, the mainstream media of misrepresenting the truth when reporting on his administration.

US academics Hunt Allcott and Matthew Gentzkow define "fake news" as "news articles that are intentionally and verifiably false, and could mislead readers."

But in fact, people have been spreading "fake news" for centuries in an effort to discredit political opponents, boost flagging circulations and even propel countries into war.

In short, "fake news" is basically "old news".

Way back then

"Since ancient Athens and Rome, lies and damned lies have always been part of political discourse," says University of Houston professor Robert Zaretsky.

Sixth century historian Procopius of Caesarea noted an "anecdota" or "secret history" of Roman emperor Justinian's private life.

Lewd details were emphasised or simply invented, perhaps to tarnish the ruler's reputation were he ever overthrown.

Later examples were made possible by technological advances such as the Gutenberg printing press that increased distribution of written materials, including 18th century "libelles," or scandal sheets that defamed French officials and personalities.

Another format dubbed "canards" helped fuel hatred of France's queen Marie-Antoinette ahead of her execution in 1793.

The trend was picked up on the other side of the Atlantic where in 1835 the New York Sun unleashed The Great Moon Hoax, falsely citing astronomer John Herschel as claiming to have discovered life there. The Sun's circulation soared.

Even the term "fake news" appears to be nothing new.

Robert Love wrote in the Columbia Journalism Review that the actual term "seems to have arisen in late nineteenth century America, when a rush of emerging technologies intersected with news gathering practices during a boom time for newspapers."

The telegraph, trans-Atlantic and trans-continental cables, linotype process and photography boosted news gathering and circulation, sometimes with ominous results.

In the late 1890s, rival publishers William Hearst and Joseph Pulitzer wanted the United States to declare war on Spain, and manipulated news from Cuba into what Love says was "the first privately funded propaganda push to war in modern media history."

The Internet age

Fast forward to the Internet age and social media has provided a fresh palette of forums, with Trump and others now denigrating unfavourable reports as "FAKE NEWS!" and worse.

On February 18, Trump tweeted: "The FAKE NEWS media (failing @nytimes, @NBCNews, @ABC, @CBS, @CNN) is not my enemy, it is the enemy of the American People!"

French academic Pascal Froissart identifies three categories of fake news: propaganda, electoral publicity, and hoaxes.

Having won the election, "Donald Trump has acquired the copyright for 'fake news'," Zaretsky told AFP.

"He uses the term to challenge not just the evidence-based claims of his critics, but to challenge the very notion of truth."

In particular, the US president seeks to disparage allegations that his campaign team colluded with Russia to win the election.

"Intelligence agencies should never have allowed this fake news to 'leak' into the public," Trump tweeted.

On March 20 he doubled down with: "This story is FAKE NEWS and everyone knows it!"

Froissart estimates Trump used the term about 40 times in the 20 weeks following his election.

"It's a winning strategy," Froissart told AFP, because his data show that tweets with the term "fake news" were repeated 14 percent more often than others and generated 89 percent more responses.

Allcott and Gentzkow concluded in a widely read study however that "fake news" during the election would only have changed vote shares "by an amount on the order of hundredths of a percentage point," far less "than Trump's margin of victory in the pivotal states on which the outcome depended."