Wikipedia's article on fattoush cites a 10th-century Arabic cookbook by Ibn Sayyar al-Warraq recording a vegetarian tharid dish reminiscent of fattoush, and a late 19th-century description by Orientalist Reinhart Dozy of a bread-based dish close to today's fattoush, with the English word fattoush first attested in 1955. No source in the article fixes when the tharid-descended bread salad became the specific dish known as fattoush, so origin-start-year and origin-end-year are left unfilled rather than guessed from the loosely related medieval precedent.
What would resolve this A food-historical study tracing bread salads in the Levant from the medieval Arabic tharid tradition through to the first clearly identified fattoush recipes, with dated textual evidence in between the 10th and 20th centuries.
Openfood historyFattoush (Wikipedia)