Shell-keep

Shell-keep - Circular or oval wall surrounding inner portion of castle; usually stores and accommodations inside the hollow walls.
Sill - Lower horizontal face of an opening.
Sleeper - Lowest horizontal timber (or low wall).

Shell-keep
round wall, usually built on top of a motte, in which the castle buildings are built up against the inner wall forming a circular courtyard
Sheriff ...

See also: Salient, Postern, Bond, Portcullis, Church