imperturbable
UK: ˌɪmpəˈtɜːbəbl | US: ˌɪmpərˈtɜːrbəbl
adj. unable to be upset or excited; calm and steady in all circumstances
The word "imperturbable" originates from Latin imperturbabilis, combining the negative prefix in- (not) with perturbare (to disturb thoroughly, from per- [thoroughly] + turbare [to agitate]). The suffix -able (capable of) was added in Late Latin, forming a term meaning "incapable of being disturbed." Over time, it evolved into Middle French imperturbable before entering English in the 16th century, retaining its core sense of unshakable calmness.
Despite the chaos around her, the CEO remained imperturbable.
His imperturbable demeanor made him an excellent negotiator.
The monk’s imperturbable silence impressed the visitors.
She faced the criticism with imperturbable confidence.
Even during the storm, the captain stayed imperturbable at the helm.