The shell bone script of character Nine
There are many explanations.
1, an arm with a hand of person
2, a brooked cave or hole
3, a kind of snake or dragon.
No matter what, most people agree that it explores an unknown area by reach as far as possible.
The bronze script of the character is
Which may the an arm, a snake or dragon, a hole, same as the shell bone script.
To me which is like a person kneeling down, and his head and arms stretching forward, searching something.
The big seal script of the character
Same as clerical script.
The Pinyin of 九 is Jiu3.