Crucially, though, existential threat was not regularly used in American public speeches in the late 20th century, despite how widely discussed existentialism itself was among the educated. In his speech on the Bay of Pigs, President John F. Kennedy referred to what we recognize as an existential threat, but did not call it one. Ronald Reagan referred to the Soviet Union as a threat, but not an “existential” one.

The “existential” add-on has jumped in this century specifically, first embraced in reference to terrorism after 9/11, and then again after the election of you-know-who in 2016. Google yielded about a million hits for existential threat in 2015, and 1,700,000 the year afterward, and 2,300,000 in 2017.

Existentialism is now one of the key shibboleths of being, or sounding, educated, summoning memories of how challengingly chilly and odd—yet clearly fundamental to human nature—The Stranger seemed when we were assigned it in college or an Advanced Placement class. Related to this is the sheer drama in the term, with its flavor of darkness. But precisely because threats of the past were not too often described as “existential,” the term existential threat feels not only highbrow and portentous, but novel.

In this way, the popularity of the term tracks a general trend in how any language changes over time. We seek to move, stimulate, and hold the attention of those we talk (or write) to, and this requires the constant renewal of words designed to grab the lapels and register our sincerity and passion. A modern example is the business-world habit of turning verbs into nouns, as in “a big ask” and “finding a solve.” The words request and solution have been around for a while and feel flat, a little vanilla. An “ask” sounds more lively than a “request” or a “bid,” even if it refers to the same thing, which is much of why this kind of usage has jumped the rails to more general parlance.

New developments like this often start in a subgroup and then spread, and today’s Democratic candidates can be analyzed as such a community, sharing not only a political aspiration, but even a certain wonkishness that would encourage the embrace of a term like existential.

But overall there is a chance element in these things, in which social history, powerful personalities, and sheer serendipity endlessly intertwine. It seems like it was just 10 minutes ago that one spoke of “tips,” “pointers,” and that which is “handy”—as opposed to the now viral usage of hack, as in life hack, cooking hack, and so on. Why are we now using that word so much? Because of the technology journalist Danny O’Brien’s coinage of it in 2005—but then, there are countless other terms that people in his profession use that most of us will never hear. One can no more know just why most new terms emerge than one can know why bell-bottoms became fashionable when they did or why men are now wearing their pants hemmed a bit higher above the ankle than they were a few years ago. Novelty is the constant; its direction and form are up for grabs.