the top is a person who moves his arms, and takes big steps, the bottom are three feet.
Let's compare it with another character in shell bone script
The two characters have the same top parts, three feet on the bottom of Rush, and one foot on the bottom of Walk.
Here the one foot or three feet means how fast the person walks or runs. One foot means slow, and three feet means fast. Or we can think that the one big foot is clear to us, three small feet let us feel a little bit blurring because the feet move so quickly, we can't see them clearly.
But in walking, we can see the feet clearly
The small seal script for Rush is
similar to the bronze script, but changed a lot.
In comparison, the small seal script for Walk is
The clerical script for Rush is
The clerical script for Walk is
No similarity to Rush any more.
I don't know why they changed from very similar to not similar at all.
The current standard printing script is
which is very similar to its clerical script.
Its pinyin is Ben1.
I need to point out that 奔 is a verb, means run if it is used alone. But it could be adverb, means ”trying hard" if it is used with 走 - walk, or other moving verbs. For example, 奔走 - walk very hard (may be very fast in compare with walking).