As a musician with the MGM Orchestra, I had friends from Argentina called "The Gauchos." They had a great show. They used the boledoras (pictured to the right) to play rhythms on the floor along with counter-rhythms with their feet. It was outrageously complicated and wonderful. They played drums, threw knives, used whips and danced. I could swear that they called their boledoras "boleos" as a shortened form. However, I cannot find this in the literature. Anyway, the boledoras were used to whip around an animals leg (instead of the lasso that North American cowboys use. I always thought that the word "boleo" came from los gauchos and not simply the word to throw (bolear). http://es.wikipedia.org/wiki/Boleadoras
I asked my friend, Lou Allard, who was a backstage worker at the MGM about what he remembered from the the Gauchos' show. He remembered the term they used as "bolas." So a throw is a "boleo" and the feminine noun of what the gaucho throws is a "bola," probably short for a "boleadora."
The ONLY reason that I think that the boleo comes from what gauchos did is because of injury on the dance floor in my experience is most often from boleos. That must be the gaucho link!
Often the gaucho would cause injury from his "boleo de la boleadora." In hunting smaller game, injury was certain. I have seen this too often on the dance floor to know that functionally it seems like a typical cowboy move on the social dance floor. Looking to catch cows or hunt small game? "¡Qué boleo, Gaucho!" [What a throw, cowboy!] One tanguera told me that her NYC tanguero told her that he was going to clear a path -- and he did with her boleos!
Before anyone takes me too seriously, Gauchos dancing tango is a Hollywood invention, I have learned. Oh darn! I spent a lot of money on my gaucho spurs in order to look authentic at the milonga. :-)
Now in all seriousness: My biggest regret, now that I have become interested in tango and Argentine culture, is WHY did I not learn more about the rhythms these amazing gauchos played!
Note: at the 4-minute mark, the Gauchos demonstrate their talents with their boleadoras.
Photo Credit: Lou Allard's copy of a signed picture of the Gauchos.
Boeadora photo -- http://en.wikipedia.org/wiki/Bolas