Two To Tango

     No one is sure how a Latin American dance first zoomed to popularity in America. Probably adapted from the beat of tribal drums in Africa, the tango in 2/4 or 4/4 time was found to be especially exhilarating by some who experimented with it.

     Many dance lend themselves to solo exhibitions. Not so the tango. This aspect of what was once a novel form of entertainment was emphasized in a popular song of the 1930s that stressed: "it takes two to tango"

     That made a vivid and emphatic way of saying that some activities require two participants. So the dance-floor expression originally came into wide use as a response to accusations of sexual misconduct. Today it has become a defense for any situation in which no one assumes full blame. 

(This is from a book called "Why We Say It")