Yesterday, President Obama gave his much-anticipated "Arab spring" speech, setting out his foreign policy objectives in the Middle East in the wake of the revolutionary wave that has shook countries from Tunisia to Bahrain. But how did we come to call this moment in history the "Arab spring," considering that the Tunisian protests that got the ball rolling started way back in December?

Of course, the "Arab spring" doesn't actually have to correspond to dates between the vernal equinox and the summer solstice, because spring is understood metaphorically and not literally. The obvious model for Arab spring is the Prague spring of 1968, when Czechoslovakia enjoyed a brief interval of democratic reform before the Soviet Union invaded. But even before 1968, spring and springtime have had a long history of usage to refer to optimistic periods of political transformation, and the same goes for equivalent terms in other European languages.

As Michael Quinion notes on his World Wide Words site, Arab spring and Prague spring have a much earlier precursor: the European revolutions of 1848, which historians dubbed springtime of the peoples or spring of nations. Those terms are translations of German Völkerfrühling and French printemps des peuples. From 1848 to 1968 to 2011, the social movements given the spring label have shared a hope for liberalization in the face of oppressive regimes.

It appears the Germans latched onto the political metaphor of springtime first. The political philosopher Ludwig Börne used the term Völkerfrühling in an article in the paper Die Wage in 1818, and as early as 1832 Börne's expression received the English translation "the People's Spring-time." When revolution struck Germany and other nearby countries in early 1848, Völkerfrühling was readily applied to the uprisings. One of the participants in the German rebellion, Carl Shurz, would later emigrate to the United States, eventually becoming a Union general in the Civil War and a U.S. Senator from Missouri. In his 1906 memoirs, Schurz recalled the Germans' "enthusiastic enjoyment of what they called the 'Völkerfrühling' — the People's Springtime." Other writers translated the expression as "The Spring of Nations."

In the twentieth century, the first political movement to earn the spring label was Russia's Liberal reform of 1904, a forerunner to the country's revolutions of 1905 and 1917. In his 1917 book The Soul of the Russian Revolution, the writer Moissaye Joseph Olgin explained that "the second half of 1904, known as 'Spring,' was marked by a strong Liberal movement." The Oxford English Dictionary's entry for spring notes that along with the Prague spring of 1968, there has been a Polish spring of 1956 (and again in 1982), and even a Seoul spring in South Korea in 1979.

In the Arab world, commentators discerned the first glimmers of political springtime well before the Tunisian demonstrations of last December. In a March 2003 New York Times Magazine piece entitled "Dreaming of Democracy," George Packer wrote pessimistically that the Iraq war was more likely to "provoke governments to tighten their grip than to ventilate the region with an Arab spring." But just two years later an "Arab spring" seemed like more than a pipe dream, with competitive democratic elections in Lebanon, Iraq, and the Palestinian territories. Egyptian political sociologist Saad Eddin Ibrahim wrote in February 2005 that these developments, along with promises of presidential elections in Egypt, "may well usher in an Arab spring of freedom, one long overdue." It would take another six years for the Arab spring to become a tangible reality in Egypt and elsewhere.

These springtime labels all owe their rhetorical power to a master metaphor that transfers the qualities of seasonal change to political change. The idea of political seasons is an ancient one: think of Shakespeare's famous opening line in Richard III, "Now is the winter of our discontent, made glorious summer by this sun of York." (The "sun of York" refers to the blazing sun adopted by Richard's brother Edward IV on his ascension to the throne, and also puns on Edward's status as a "son of York," since he was the youngest son of the Duke of York.) But I can't help thinking of the wonderful movie Being There, adapted from Jerzy Kosinski's satirical novella. Peter Sellers stars as a simple-minded gardener named Chance who, through a series of mistaken impressions, is thought to be a profound economic thinker. Here he is talking seasons with the president (Jack Warden) and his confidant, a wealthy businessman (Melvyn Douglas).