It’s original name was Fort Duquesne. Before that it was Fort Prince George. The Fork area had been inhabited by natives before. In 1753 a certain Lt. Colonol George Washington convinced Virginia Governor Robert Dinwiddie that the Forks of Ohio region was an important location strategically into the western interior.
Dinwiddie ordered the construction of a Fort at the location where construction began on Fort Prince George. It was short lived as a French army under Contrecœur of 500 soldiers and a comparable number of Indians invaded the Forks region on task to build a chain of forts to secure the Great Lakes region in their interest. The occupants of Ft. Prince George were quickly evicted and construction of Fort Duquesne (named after the Marquis Duquesne Governor of New France (Canada)).
The Crown got the last laugh as the French ended up handing the Fort over to the British as a consequence of losing the Seven Years War. The Britts promptly named the fort after Sir William Pitt and the Americans named the city that grew around the fort “Pittsburgh”.