As a native Jacksonian, I can assure you that Jackson was indeed called "Chimneyville ".
Perhaps the gentleman from Massachusetts should review our acclaimed historian,
Grady Howell, Jr.'s 2007 book :

"Chimneyville, 'Likenesses' of Early Days in Jackson, Mississippi,”

A quote from Mr. Howell's book:

A Union soldier described the ruins, “The Jackson of February, 1864, was not the Jackson of May, 1863.
Then it was a beautiful city; now it is a heap of ruins. Some of the citizens called it ‘Chimneyville’ from
the great number of standing chimneys from which the buildings have been burned.”

An illustrated review of his work can be viewed at this link: