Marilyn Loden hadn’t planned to make history when she spoke on a panel at the 1978 Women’s Exposition in New York.

She wasn’t even supposed to be there.

Loden, then 31 and a mid-level manager at New York Telephone Co., was asked to attend the exposition after the company’s only female vice president couldn’t make it. Four other women joined Loden on the panel titled “Mirror, Mirror on the Wall.” The name was fitting, Loden recalled, because the discussion centered on how women, and their self-image, were to blame for their lack of advancement in the workforce.

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When Loden’s turn came to speak, she thought about how she had been tasked with at her company to explore why more women weren’t entering management positions. She had gathered enough data that she felt confident the problem extended beyond what her colleagues were wearing or saying.

“It seemed to me there was an invisible barrier to advancement that people didn’t recognize,” Loden said.

That day, she called it the “glass ceiling.”

May 24 will mark 40 years since Loden coined the phrase and, in many ways, it remains as relevant as it did during a time when women were changing long-accepted gender norms in schools, homes and offices. Over the years, the term has become universally recognized shorthand for a complex problem and has been uttered by some of the most well-known women in modern history, including Madeleine Albright, Aretha Franklin and Oprah Winfrey.

Hillary Clinton turned to the phrase for two notable speeches.

“Although we weren’t able to shatter that highest, hardest glass ceiling this time, thanks to you, it’s got about 18 million cracks in it and the light is shining through like never before,” Clinton said in 2008 after her first failed presidential bid.

Then in 2016, during her concession speech to President-elect Donald Trump: “Now, I know, I know we have still not shattered that highest and hardest glass ceiling, but someday, someone will.”

The country’s word gatekeeper, Merriam-Webster, defines glass ceiling as “an intangible barrier within a hierarchy that prevents women or minorities from obtaining upper-level positions.”

It lists the phrase’s origin as 1984, the same year, incidentally, the words “date-rape,” “horndog” and “womanism” were born.

An origin date is fluid and only reflects when a term appeared in print, said Merriam-Webster editor Peter Sokolowski. (A side note for logophiles: Because the word “shithole” appeared in The Washington Post and numerous publications after President Trump recently used it, Sokolowski said it just got closer to being included in the dictionary).

In 1984, the phrase “glass ceiling” appeared in an AdWeek article and in 1986, the Wall Street Journal used it in a headline. In 1993, the term was first printed in the Merriam-Webster Collegiate Dictionary, marking a “relatively quick” pace from its inception, said Sokolowski.

“That shows there was a need for a specific term that meant something like this,” he said. “Now you can say ‘glass ceiling,’ and we all understand precisely what it means.”

Loden kept the letter she was sent about speaking at the Women’s Exposition, which was billed as the “first national dialogue on women at work.” She also saved the program, which lists discussions on topics ranging from sexism to alcoholism over two days at the Roosevelt Hotel. The titles of some of the panels: “All That Glitters,” “Hire Him, He’s Got Great Legs!” and “Becky Wants to be a Plumber.”

Loden’s “Mirror, Mirror” was described as a discussion of  “messages of limitation which confront women and the effect on aspirations.”

One of the panelists was Holly Knox, who founded Peer, an advocacy organization that aimed at fighting sexual discrimination in schools. At the time, girls were still relegated to home economics classes, and it mattered little whether they had athletic abilities because no sport scholarships existed for them. In schools, most teachers were women, but the vast majority of principals were men.

Knox, now 71, said she doesn’t remember sitting on the panel with Loden. But she said the many advances women have made since 1978 make the term “glass ceiling,” in many ways, even more relevant now.

“There are more women looking up at the glass ceiling today,” Knox said. “That was one of the main contributions of the women’s movement back in those days. We all started seeing something new. In the ’50s when I was a kid, women didn’t see, they didn’t look, they didn’t say, ‘Hey, how come I can’t do that?’ ”

Knox marched in Washington in the 1970s, and she marched in the nation’s capital again in 2017 after the presidential inauguration.

Loden, who has written three books, said much has changed from when she worked for one supervisor who used to tell her to smile more and another who invited John Molloy, the author of “Dress for Success,” to assess women supervisors’ attire and tell some why they were never going to make it. But even today, she said, not enough women and people of color are reaching leadership ranks, and some workplaces still don’t take sexual harassment and predatory behavior seriously.

“When I read about #MeToo and the sort of wave of people acknowledging what’s been going on, it strikes me that there’s still a lot of fear about challenging the status quo,” Loden, now 71, said.

On the day of the women’s exposition, Loden said, she hadn’t written a speech. Instead, she said, the term — which was in the same breakable vein as the mirror metaphor — came to her as she spoke.

“To be honest with you, I didn’t think it was a big deal,” she said. “It made sense to me in the moment.”

Afterward, she said, women in the audience came up to her, wanting to talk about how they had done everything right and still found themselves stalled. It was that sentiment, supported by data she had collected, that Loden took with her into a meeting to inform her male supervisors about why women weren’t advancing at the company. There was no evidence, she told them, to support the assumptions that women did not have the skill sets or the temperament to do so — a conclusion, she said, that made her unpopular. She left the company when she was later ordered to take a job she didn’t want after 12 years of working there.

Since then, Loden has worked as a consultant on diversity and gender issues for companies, the military and professional organizations.

“I thought I would be finished with this by the end of my lifetime, but I won’t be,” Loden said. She has accepted that the term “glass ceiling” will remain needed for a while longer. “I’m hoping if it outlives me, it will [become] an antiquated phrase. People will say, ‘There was a time when there was a glass ceiling.’ ”

If language is a gauge of progress, there may be cause for optimism in the “word of the year” Merriam-Webster chose for 2017. It speaks more to the possibilities of women than to the limitations, and Sokolowski said it was chosen based on spikes seen in online searches after three events: the Women’s March, the release of “Wonder Woman” and the uncovering of sexual assault allegations against Hollywood mogul Harvey Weinstein.

The word was “feminism.”

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