serenity

noun, plural se·ren·i·ties for 2.

1. the state or quality of being serene, calm, or tranquil; sereneness.
2. (usually initial capital letter) a title of honor, respect, or reverence, used in speaking of or to certain members of royalty (usually preceded by his, your, etc.).

noun plural -ties

1. the state or quality of being serene
2. (often capital) a title of honour used of certain royal personages: preceded by his, her, etc

n.1530s, of weather, 1590s, of persons, from Middle French sérénité, from Latin serenitatem (nominative serenitas) “clearness, serenity,” from serenus (see serene). Earliest use (mid-15c.) was as a title of honor for kings, probably from the similar use of Latin serenitas, applied to Roman emperors, later popes.