The waltz, (from German walzen, “to revolve”), is a highly popular ballroom dance that evolved from the Ländler in the 18th century. Characterized by a step, slide, and step in 3/4 time, the waltz, with its turning, embracing couples, at first shocked polite society. It became the ballroom dance par excellence of the 19th century, however, and tenaciously maintained its popularity in the 20th.

Source: Encyclopedia Britannica