Kinu' usually means that men's uchiginu (inner garment) or women's kasane-uchiki (a series of brightly colored unlined robes), thus kinu might be a so-called tarikubi (a type of kimono collar, hang-down collar) but there is no reliable evidence.
「衣」(きぬ)といえば普通は男子の内衣や女子の重ね袿をさすので、いわゆる垂頚(着物襟)だったと思われるが、確証はない。