PLACIDITY
repose, quiet, placidity, serenity, tranquillity, tranquility
(noun) a disposition free from stress or emotion
placidity, placidness
(noun) a feeling of calmness; a quiet and undisturbed feeling
Source: WordNet® 3.1
Etymology
Noun
placidity (usually uncountable, plural placidities)
The state of being placid; peacefulness.
Synonyms
• (state of being placid): composure, peacefulness, serenity
Source: Wiktionary
Pla*cid"i*ty, n. Etym: [L. placiditas: cf. F. placidité.]
Definition: The quality or state of being placid; calmness; serenity.
Hawthorne.
Source: Webster’s Unabridged Dictionary 1913 Edition