When “asil” was first used to refer to Arab horses

Yesterday, Hylke and I were discussing when the word “asil” (authentic, original in Arabic) first came to be used in reference to Arab horses, and by whom. I do not believe Bedouins were the first to use the term to refer to their own horses. Even today, they seldom do. Rather, I believe it is a word urban dwellers of Damascus, Aleppo, Bagdad or other cities first applied to some of the horses of the Bedouin to differentiate them from horses of unknown origin and provenance (kadish). Hylke believes the spread of the word “asil” as applied to horses is connected to Orientalism, to European views of racial superiority and to the idea of “purity of blood”, applied to Arabian horses. That would have come about sometime during the nineteenth century. She believes the word was picked up by Syrian/Egyptian/Ottoman horse merchants, traders and other townfolks in response to European emphasis on “pure blood”. It would be nice to find the earliest written reference to the use of the word “asil” in reference to Arab horses in Western equine and travel literature, but also in contemporary Arabic or Ottoman Turkish writings.