Glass ceiling spiked on June 7th and 8th after primary victories in several states made Hillary Clinton the presumptive Democratic nominee for president. The phrase spiked again on July 27th when she officially became the first woman to be nominated for president by a major party.
Eight years ago to the day, in a concession speech following her loss to President Obama in the 2008 primaries, Clinton said:
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.
Glass ceiling means “an unfair system or set of attitudes that prevents some people (such as women or people of a certain race) from getting the most powerful jobs.” It is a very recent idiom in English, dating back only to 1984. According to the Oxford English Dictionary, the first use of the term had to do with advancement in the corporate management structure:
Women have reached a certain point—I call it the glass ceiling. They're in the top of middle management and they're stopping and getting stuck.
—Adweek, 15 March 1984
By coincidence, 1984 was the year that Geraldine Ferraro was nominated as the Democratic vice-presidential candidate on a ticket with Walter Mondale.