I've always wondered about this ... an excerpt from the Forward:

That much I knew. Still, I wasn’t prepared for the surprise of finding out what the origins of “hora” are, or how much history comes with them.

I won’t keep you in suspense: “Hora” comes from ancient Greek khoros, which also gives us such words as “chorus” and “choir.” Traditional circle dances deriving their names from khoros can be found all over the Balkans and southeastern Europe. They include the Turkish and Romanian hora, the Bulgarian horo, the Montenegrin and Macedonian ora, and the Russian khorovod, and they are all very old and highly similar in the way they are danced.

True, our own modern associations with the ancient Greek chorus have nothing to do with horas. They come from the performances that we have seen of Greek tragedy, in which the chorus consists of several actors who comment on the dramatic events taking place. On the ancient Greek stage their lines were commonly sung rather than declaimed, which is why a chorus, or choir in modern European languages, is an ensemble of singers.

But dramatic tragedy and its chorus were late features of ancient Greek culture. A khoros was originally a dance, generally performed in honor of the gods at religious celebrations. The great plays of such tragedians as Aeschylus, Sophocles and Euripides were an outgrowth of the much simpler Attic drama, itself a development of the khoros kyklikos, the annual circle dance performed in Athens at the festival of the god Dionysus. In the beginning, Attic drama had only one actor who spoke or sang, which he did at moments when the dancing stopped. It was only gradually that the entire khoros assumed this role.

Moreover, Greek tragedy was specific to Athens. Everywhere else in ancient Greece, each village had its own religious celebrations with circle dances, and these khoroi eventually lent their name to similar dances in adjacent areas. When Christianity replaced paganism, they were transferred to Christian holidays. In Romania, well into the 20th century, it was customary for horas to be danced in town squares, outside the local church, on Easter Sunday, as well as at weddings and other celebrations. In modern times, special horas, with their melodies and words, were composed and danced for specific occasions, like the famous “Hora Unirii,” “the Hora of the Union,” which became a Romanian patriotic song after it was written to celebrate the union of Wallachia and Moldavia that formed modern Romania in 1859.

The first “Jewish” hora — that is, the first hora introduced into Palestine — was also composed and choreographed (that’s another word deriving from khoros!). The choreographer was the Romanian Jewish dancer Baruch Agadati, who got together in 1924 with a composer and writer of lyrics and created a hora for a show put on by the Ohel Theater Company, which toured with it in the pioneering settlements of the Valley of Jezreel. “Hora Agadati,’ as it became known, was an instant hit.