One that has recently or suddenly risen to an unaccustomed position of wealth or power and has not yet gained the prestige, dignity, or manner associated with it.

(French, from past participle of parvenir to arrive.)

Within a few years the seals were found only on the outer rocks & the “sealers” too turned to farming potatoes, sheep & pig rearing… These parvenu farmers clear the land by bushfires that smolder beneath the peat for many seasons, surfacing in dry spells to sow renewed calamity.

Definition from Merriam-Webster