Q:

Is Ussop based on Aesop?

Aesop was an Ancient Greek fabulist or story teller credited with a number of fables now collectively known as Aesop's Fables. Here is a description of Aesop: 

"of loathsome aspect... potbellied, misshapen of head, snub-nosed,
  swarthy, dwarfish, bandy-legged, short-armed, squint-eyed,
  liver-lipped—a portentous monstrosity,"

Here are somethings that they have in common. 

They both tell fictitious stories.
They both have liver-lips.
Their names are pronounced the same.

I believe that Ussop might be a combination of Pinocchio and Aesop.

A:

Ussop's name is probably based on "Isoppu" which is the Japanese pronunciation of Aesop. (One Piece Wiki)

The Wiki also claims "uso" means "lie" in Japanese so Ussop is a combination of "liar" and "storyteller" (Aesop). Basically this says it is likley but the source is not at all canon. We don't know as Oda hasn't definitively said, but probably.

