Noun. From French, "petite" meaning
small, the petite bourgeoisie is the lower middle class, especially tradesmen such as
shopkeepers and
artisans. In the English language, the use dates back to 1916.
In French, the term bourgeois (old form: burgeis) is known as far back as 1080. La moyenne bourgeoisie is the "middle middle class" and the upper middle class is referred to as la grande bourgeoisie or la haute bourgeoisie thanks, mirv.
Also, referring to something as "petit-bourgeois" (adj.) is more often than not pejorative, alluding to narrowmindedness and mediocrity.
Main sources: Merriam-Webster online, Le nouveau petit Robert