What is the origin of unshakable

stoicism, the

stoic adj. 'following the philosophy of the Stoa' (15th century), 'self-controlled', hence also 'unshakable, indifferent' (17th century), from Latin stōicus, Greek stōïkós (στωϊκός) 'the philosophy of Concerning Stoa, belonging to it ', substantives' Stoic', derived from the Greek stoá (στοά) or stōïá (στωϊά) 'column, pillar, portico, portico' or the one named after it (Stoa), from Zenon and Kition 308 BC u. Z. in Athens in the portico poikílē (brightly painted ’) stoá founded philosophy school, whose philosophy demands unshakable equanimity of the soul in all situations of life from its followers. Stoic with ‘followers and representatives of the Stoa, indifferent, imperturbable human being’ (17th century; as early as the 15th century, Latin Stoicus in German texts). Stoicism m. ‘Doctrine and worldview of the Stoa, equanimity, imperturbability’ (18th century); see French stoïcisme (17th century).