Both Uses

provincial
in
The Great Gatsby
(Edited)

But young men didn't — at least in my provincial inexperience I believed they didn't — drift coolly out of nowhere and buy a palace on Long Island Sound.
p. 49.4 *

provincial = unsophisticated
Then he went into the jewelry store to buy a pearl necklace — or perhaps only a pair of cuff buttons — rid of my provincial squeamishness forever.
p. 179.4

Definitions:

(1) (provincial as in: the provincial license)
of a province (a geographic administrative area); or related to parts of the country that are outside of major cities
(2) (provincial as in: provincial attitude)
unsophisticated (meant disapprovingly to refer to old-fashioned or narrow-minded attitudes and ideas)

This meaning originated as a pejorative term for ideas held in the provinces that were considered old-fashioned or uninformed by many who lived in the capital city.
(3) (meaning too rare to warrant focus)
French Provincial refers to a style of architecture, furniture, or design that originated in the French countryside in the 17th and 18th centuries.