tarantella: [18] In the 15th century in southern Italy an epidemic of a curious nervous disorder broke out, one of whose symptoms was an uncontrollable compulsion to whirl and cavort around, as if dancing. The people attributed it to the bite of a spider, the tarantula [16], named after the local town and seaport of Taranto. In due course the dancing came to be rationalized as a method of counteracting the effects of the spider’s bite, and it was named tarantella, a diminutive form of Taranto. The word finally came to stand for a particular type of dance.
tarantella (n.)
1782, "peasant dance popular in Italy," originally "hysterical malady characterized by extreme impulse to dance" (1630s), epidemic in Apulia and adjacent parts of southern Italy 15c.-17c., popularly attributed to (or believed to be a cure for) the bite of the tarantula. This is likely folk-etymology, however, and the names of the dance and the spider more probably share an origin in Taranto, the name of a city in southern Italy (see tarantula). Used from 1833 to mean the style of music that accompanies this dance, usually in 6/8 time, with whirling triplets and abrupt major-minor modulations. Related: Tarantism.