"Déjà vu means “already seen” in French, a term possibly coined by French philosopher Émile Boirac in a letter to the editor of Revue Philosophique de la France et de l'Étranger in 1876. Boirac speculated that perhaps residues of long-forgotten perceptions triggered the feeling. There is now some laboratory evidence that vague similarities between one scene and another can indeed lead to déjà vu."
https://www.scientificamerican.com/article/what-causes-the-feeling-of-deja-vu/