The primitive "upside down in a row" is odd to me. Anyone know the real meaning of it? or can shed any light on it what so ever? Thanks.

According to zhongwen.com it's a pictograph of branches and foliage:

http://zhongwen.com/d/183/d126.htm

But my 漢和 dictionary says that the entire 業 character is a pictograph of a wooden stand for a certain musical instrument.

Interesting. Thanks.