|Noah Webster's Dictionary|
1. (n.) The quality or state of being serene; clearness and calmness; quietness; stillness; peace.
2. (n.) Calmness of mind; evenness of temper; undisturbed state; coolness; composure.
Serenity (1 Occurrence)
Job 29:24 If I laughed on them, they believed it not; and they troubled not the serenity of my countenance. (DBY)