Sill

Sill (D.Eng. syl, Mid. E. sylle, selle; the word appears in Icel. syll, svill, Swed. syll, and Dan. syld, and in German, as Schwelle;  Skeat refers to the Teutonic root swal-, swell, the word meaning the rise or swell formed by a beam at a threshold; the Lat. solea, from which comes Fr. seuil, gives Eng. "sole," also sometimes used for "sill"), the horizontal base of a door or window-frame. A technical distinction is made between the inner or wooden base of the window-frame and the stone base on which it rests - the latter being called the sill of the window, and the former that of its frame. This term is not restricted to the bases of apertures; the lower horizontal part of a framed partition is called its sill. The term is sometimes incorrectly written "cill." (See MASONRY.)