1911 Encyclopædia Britannica/Sill (door)

SILL (O.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.)