From the form of "太", we can see that it is composed with "大" and an indicator . It is a bit hard to guess its meaning, let us examine its evolution history first: ( image get from http://www.vividict.com )
Learn one Chinese Character a day - 太
In Oracle Script period, it is possible that there was only "大". When time passed, it was necessary to have a word to mean something extreme big or bigger than big, Chinese ancestors added a below 大, to get . The image depicts that even earth is smaller comparing with the above. So is to mean something very big. Eventually the was then simplified to be .
太 means extreme big, it is extended to mean extreme, super, or very as well. Now it is time to enjoy a Chinese calligraphy with 太 inside: