Late 15th century; earliest use found in Acts of Parliament. From Anglo-Norman niais, niés, nieys, nioys, adjective and noun (in falconry), Middle French niais, adjective (1210–25 in Old French as nies in sense ‘energetic’ (of a sparrowhawk), 13th cent. in sense ‘foolish, naive’ (of a person)), noun from an unattested post-classical Latin adjective from classical Latin nīdus nest. Compare Italian nidiace, Old Occitan niaic, nizaic.