Lionheart was referred to as my lord Yea and Nay. This was because of his manner of making swift decisions and answering briefly, 'Oc'. Certainly not because he was indecisive.
Langue d'oïl was the language used in the northern part of France, and was the Norman-French understood in England - unless you were English, in which case one spoke Anglosaxon! The word 'oïl' is now pronounced 'Oui' the French for yes.
The 'English' were defeated in 1066 by William the Conqueror, Duke of Normandy. Few Norman overlords spoke English. The result of Prince John losing almost all his continental fiefs was that the nobles had to stay in England and learn to converse properly with their subjects. This resulted in the crash-job we now call English. Er, I mean the rich and varied language we speak today.
Below is the start of a song in Occitan composed by Guillaume de Poitiers. A famous troubadour (and for forty years Duke of Aquitaine until AD 1126 - which helps the longevity of one's songs). Beneath is the French translation and one can see the similarity - and the similarity to Spanish.