A few years back, when RCA records issued a boxed set of 100 favorite Boston Pops recordings made by Arthur Fiedler, they included Handel’s celebrated “Largo.”

Over a hundred years earlier, the Theodore Thomas Orchestra had established this melody as a favorite with 19th century American audiences. Back then, Handel was best-known for his sacred oratorios, and his “Largo” acquired a kind of honorary “halo” by association. Also, the Italian text for the melody began “Ombra mai fui,” and since “ombra” meant shade, many music lovers probably assumed it had something to do with the dear departed shade or spirit of a loved one—hence its melancholic solemnity.

In fact, this melody originated in a decidedly secular, downright whimsical context: as the opening aria of an opera by Handel that premiered in London on today’s date in 1738. The opera was entitled “Xerxes,” and dealt with the real-life Persian King who invaded ancient Greece. In the writings of the Greek historian Herodotus, Xerxes is depicted as an all-powerful despot, whose every whim became law. As evidence of the irrational effect of absolute power, Herodotus tells of Xerxes’ fondness for a certain plane tree that he ordered decorated with gold ornaments and put under perpetual military guard as a sign of royal favor. In Handel’s opera, the famous “Largo” is actually Xerxes’s dreamy song to this famous tree—and the “shade” referred to is the sort to be found under its gold-bedecked branches.