OF meaning in Regional ?

Old French (franceis, françois, romanz; Modern French: ancien français) was the language spoken in Northern France from the 8th century to the 14th century. Rather than a unified language, Old French was really a linkage of Romance dialects, mutually intelligible yet diverse, spoken in the northern half of France.

In the 14th century, these dialects came to be collectively known as the langue d'oïl, contrasting with the langue d'oc in the south of France. During the mid-14th century, one of the dialects of Old French, namely Francien from Île-de-France area, transitioned to Middle French, the language of the French Renaissance – itself a predecessor to modern French. As for other components of Old French, they evolved into various modern languages (Poitevin-Saintongeais, Gallo, Norman, Picard, Walloon, etc.), each with its own linguistic features and history.

The region where Old French was spoken natively roughly extended to the northern half of the Kingdom of France and its vassals (including parts of the Angevin Empire, which during the 12th century remained under Anglo-Norman rule), and the duchies of Upper and Lower Lorraine to the east (corresponding to modern north-eastern France and Belgian Wallonia), but the influence of Old French was much wider, as it was carried to England and the Crusader states as the language of a feudal elite and commerce.