And a similar word:

"In Ancient Greek philosophy, ataraxia (Greek: ἀταραξία, from "a-", negation and tarachē "disturbance, trouble") is a lucid state of robust equanimity characterized by ongoing freedom from distress and worry. In non-philosophical usage, ataraxia was the ideal mental state for soldiers entering battle. Achieving ataraxia is a common goal for Pyrrhonism, Epicureanism, and Stoicism, but the role and value of ataraxia within each philosophy varies in accordance with their philosophical theories."