Why is a potential core region of a jet called a potential core ?

[fayaazhussain]

Why is a "potential core" region of a jet called a "potential core"?

We all know that there exists a region called "potential core" in a jet where there are no mean velocity gradients. My question is, why is it called a "potential" core?

 

[boneh3ad]

It obeys potential flow rules, aka it is essentially inviscid.