Amos said:

I b'leeve the 00 was designed as a lady's "parlor" guitar back before telbinision ruled the evening.

Actually, it was the monster of its day.

Martin originally numbered its guitars by size, from 5 to 1. A five was the smallest size, one the largest. When they decided to make a guitar even larger than a one, they, logically enough, sized it a zero. As they made even larger ones, they went to the double- and triple- zeros. The dreadnought came after that.

Peter.