Donald Trump’s deep insecurity about his "short fingers," explained

There are two criticisms Republican presidential frontrunner Donald Trump absolutely cannot tolerate. The first is that he isn't as rich as he claims to be. The second? Call Trump a racist or a bully or a xenophobe if you must, but do not, under any circumstances, insult the length of his fingers.

Last week, Sen. Marco Rubio did just that: "I don't understand why his hands are the size of someone who is 5-foot-2," Rubio said of Trump, adding: "And you know what they say about men with small hands? You can't trust them."

That isn't actually what they say about men with small hands, but we'll get to that in a minute.

Rubio didn't pick his insult at random. Trump's sensitivity about his short fingers has a long, entertaining, very Trump-like backstory — one that, like so much of the 2016 presidential race, has its roots in the early 1990s.

Why Trump really hates the insult "short-fingered vulgarian"

Accusations of below-average finger size have dogged Trump for nearly 30 years. In 1988, Spy, a satirical magazine based in New York, coined an epithet for Trump that it would gleefully repeat for eight years: "short-fingered vulgarian."

Spy, which was published from 1986 to 1998, was busy skewering celebrities and public figures as Trump was building his national profile. Proudly avaricious and braggadocious, Trump embodied the spirit of the '80s. And Spy made him a frequent target of not just insults but also elaborate practical jokes.

"Donald Trump was our clickbait," Bruce Feirstein, a contributing editor for Spy, wrote for Vanity Fair in 2015:

He brought us word-of-mouth recognition, and more readers—just the same way he is now bringing eyeballs to newscasts, and page views to Web sites… Over the course of our years at Spy, we fact-checked his books and his finances (with predictable results), trolled him by sending miniscule checks — as low as 13 cents —to see if he’d cash them (he did), and wrote up his all-but-forgotten business debacles. (Remember the "Trump Castle World Power Boat Championship"?)

"Two-month anniversary of the publication of short-fingered vulgarian Donald Trump's The Art of the Deal," Spy noted in January 1988, its first use of the phrase. "Reader … is rushed to the hospital with hubris shock." (The same issue, presciently, floated the possibility of a Trump presidential bid, citing a survey that found 4 percent of Americans were sad he wasn't in the running.)

Spy would call Trump a "short-fingered vulgarian" 12 times in the next eight years, including once reprinting a correction from the Stanford student newspaper, which had written the phrase as "short-fingered Bulgarian" and had to apologize for insulting Bulgarians.

Trump, an expert troll, was getting trolled. He rose to the bait, responding in characteristic fashion: scribbling on the article in Sharpie marker and sending it to its writers. ("Face of a dog!" he once wrote over a photo of New York Times columnist Gail Collins, who had committed the other ultimate infraction: downplaying Trump's wealth by calling him a "thousandaire.")

What upset Trump wasn't being called a "vulgarian," a rich person with bad manners. It was the slur on his finger length.

"To this day, I receive the occasional envelope from Trump," Graydon Carter, a founder of Spy and now the editor of Vanity Fair, wrote in 2015.

"There is always a photo of him — generally a tear sheet from a magazine. On all of them he has circled his hand in gold Sharpie in a valiant effort to highlight the length of his fingers. I almost feel sorry for the poor fellow because, to me, the fingers still look abnormally stubby."

Rubio's "small hands" joke was probably a slur on Trump's penis size

Before we get any further into the saga of Trump's hands, here's one important note: It is not at all clear that Trump's fingers are, in fact, unusually short. But what matters is that Trump himself seems to believe short-fingeredness is a terrible accusation that must be refuted.

The Washington Post's Philip Bump conducted a thorough investigation that included, among other things, the photographic concept of foreshortening, a 1902 study of the finger lengths of imprisoned criminals, and a comparison of the size of Trump's hands with the size of a sheet of paper.

Bump's conclusion: "Trump is not a 'short-fingered vulgarian,' for the sole reason that he is not short-fingered."

Still, Trump seems to take a slur on his fingers as a terrible insult, for reasons that Spy was far too arch to make explicit.

Palm readers, for one, have a host of stereotypes about short-fingered people: They're impulsive, stubborn, unconcerned with detail, prone to jumping to conclusions, and interested above all in doing big things. ("They build enormous buildings," the Benham Book of Palmistry even notes.) But while that's a scarily accurate description of Trump, it's unlikely this is what Spy meant.

Finger size also could be linked to testosterone, and has been cited as a predictor of everything from athletic prowess to ruthlessness on a trading floor. But that research — which, in any case, was conducted long after Spy first called Trump short-fingered — deals with the ratio of the length of a man's ring finger to the length of his index finger, not how long or short the fingers in question are.

Trump was probably drawing a much less obscure conclusion: He thought Spy was implying he had a small penis. "My fingers are long and beautiful, as, it has been well documented, are various other parts of my body," he told the New York Post's Page Six in 2006. "From what I hear, the same cannot be said of editors of the failed Spy."

Trump, as Trump does, was making the subtext text. "Other parts of [his] body" are definitely what it seemed Marco Rubio was insulting, too, when he made fun of Trump's small hands.

Rubio claimed they were a sign of untrustworthiness — but while there are some superstitions linking hand size to strength of character, a far more common association is that small hands are an indication of, um, smallness elsewhere. (Urban Dictionary was on the case in 2008: "If you say someone has small hands it means that they have a small penis.")

And Rubio's remark has put the old jokes about Trump's hand size back into circulation:

It might set Trump's mind to rest if it were more widely known that the connection between hand size and penis size is spurious at best. The connection has been studied twice, once finding only a weak correlation and once finding no relationship at all.

But the feud over whether Trump is a "short-fingered vulgarian" has now lasted nearly 30 years. It would be a shame to stop it now.