Still"ness (?), n.
The quality or state of being still; quietness; silence; calmness; inactivity.
Painting, then, was the art demanded by the modern intellect upon its emergence from the stillness of the Middle Ages.
J. A. Symonds.
Habitual silence or quiet; taciturnity.
The gravity and stillness of your youth
The world hath noted.
© Webster 1913.