Why the inspirational words of a historic or cultural icon that you’re sticking on Instagram right now more than likely belong to someone else .

There’s something solid and comforting about a good quotation. Authors throw them into the front of novels to give them a little more weight. Politicians use them in speeches to make themselves sound that little bit more wonderful. Then, of course, there are the thousands of people, these days, who post them on Instagram, with the apparent mission of seeding inspiration into the world (the real goal being to get more followers).

Unfortunately, as it turns out, even some of our most treasured quotes – like some of our most shared news stories – are not exactly, how to put it… real. In fact, whether it’s because they’ve been warped, misattributed or made up completely, many quotes widely in use today are not at all what they seem, according to self-proclaimed “quote investigator” and author of Hemingway Didn’t Say That, Mr Garson O’Toole. As he writes in the introduction to this tome, the phenomenon is particularly prevalent in the internet age. “Search engines contain link after link to websites with faulty information, repetitive text and incomplete data,” he says. “Moving beyond this mélange of misinformation is nearly impossible for the average web user. It’s no wonder, then, that such mistakes are perpetuated and duplicated to the extreme.”

In Hemingway Didn’t Say That, Mr O’Toole trains his analytical eye upon a series of well-loved quotations to find their true and unexpected origins. Famous names whom we discover to be not quite as pithy or witty as we thought include Ms Marilyn Monroe, Emperor Napoleon Bonaparte and (probably one of the most misquoted men ever), Mr Mark Twain. As a taster of what’s in store, scroll down for our five favourite examples, and prepare to subtly rewrite that best man’s speech.

Mr Thomas Edison

Not only is this quote a rather irritating one, frequently dispensed by people who just want you to shut up and get on with whatever you’re doing, it wasn’t originated by the inventor of the electric light bulb. Mr O’Toole finds an earlier version of the phrase attributed to Massachusetts lecturer Ms Kate Sanborn in 1892, several years before it was ever mentioned by Mr Edison.

Mr Pablo Picasso

This was an attribution given by Mr Steve Jobs in a 1988 interview with Australian newspaper The Sydney Morning Herald, which has since been repeated (because no one would expect Mr Jobs to make a mistake). But Mr Pablo Picasso never said it, writes Mr O’Toole. In fact, though Mr TS Eliot produced a formulation of the idea in the early 20th century, he didn’t use those exact words. His words got mangled, and have been attributed to everyone from obscure humourists to the composer Mr Igor Stravinsky. Even then, not Mr Picasso.

Mr Ernest Hemingway

If you’ve ever been to a creative writing class, you’ll have heard this one. The legend goes that Mr Ernest Hemingway came up with this half-sentence for a bet in which he claimed he could write a story in six words. Mr O’Toole notes, however, that usage only begins in 1991, and the earliest example connecting Mr Hemingway to the phrase is from a 1988 play, Papa, by Mr John De Groot, which presents a fictionalised version of Mr Hemingway’s life.

Mr John Lennon

Mr John Lennon did indeed say this, in the song “Beautiful Boy (Darling Boy)” from his 1980 album Double Fantasy. “Ever since,” writes Mr O’Toole, “Lennon has been credited with the saying on all sorts of inspirational bric-a-brac.” But the earliest example he finds of the quote is in a 1957 issue of Reader’s Digest, in a section called Quotable Quotes. Imagine.

Spider-Man/Voltaire

No, there aren’t that many similarities between the web-slinging superhero and the leading wit of the French Enlightenment. But neither of them was the originator of this phrase. Mr O’Toole traces it, instead, to a rather dry collection of decrees made by the French National Convention in 1793. It passed from there, through the lips of world leaders, including Sir Winston Churchill and Mr Franklin D Roosevelt and… Spidey. But only in 1962.

Hemingway Didn’t Say That: The Truth Behind Familiar Quotations (Little A) by Mr Garson O’Toole is published on 1 April