From Middle French petit, English since the late 14th century. The disparaging meaning develops during the 16th century.
Middle English petifrom Old French variant ofpetitpetit
American Heritage Dictionary of the English Language, 5th Edition
Petty Sentence Examples
All the petty supervising establishments are composed of convicts.
In Wischau itself, a petty German town, Rostov saw the Emperor again.
They acted also as police courts in the case of petty thefts, breaches of the peace and the like.
He had annihilated the petty kings of the South, had crushed the aristocracy, enforced the acceptance of Christianity throughout the kingdom, asserted his suzerainty in the Orkney Islands, had humbled the king of Sweden and married his daughter in his despite, and had conducted a successful raid on Denmark.
Behind the College is the Royal Hospital School, where woo boys, sons of petty officers and seamen, are boarded.