imperturbable

adj

Etymology: PIE word *né From Late Middle English imperturbable (“undisturbed; impossible to disturb”), borrowed from Late Latin imperturbābilis, from Latin im- (variant of in- (prefix meaning ‘not’)) + Late Latin perturbabilis (“perturbable”) (from Latin perturbō (“to confuse; to alarm, disturb, trouble, perturb”) + -bilis (suffix forming adjectives denoting a capacity or worth of being acted upon)). Perturbō is derived from per- (intensifying prefix) + turbō (“to agitate, disturb, unsettle, perturb; to upset”) (from turba (“disorder, disturbance, turmoil”) (possibly from Ancient Greek τῠ́ρβη (tŭ́rbē, “confusion, disorder, tumult”), either from Pre-Greek, or Proto-Indo-European *(s)twerH- (“to agitate, stir up; to urge on, propel”)) + -ō (suffix forming infinitives of regular first-conjugation verbs)). By surface analysis, im- (prefix meaning ‘not’) + perturbable.

1. Not capable of being, or not easily, perturbed, excited, or upset; calm and collected, even under pressure.

   “[T]o a vviſe man there can happen no iniury or offence at all, to moleſt the felicity of his minde, vvhich (in the Stoicks opinion) ought to bee imperturbable, and his heart adamantine.”

   “[T]he good Dominie bore all his disasters with gravity and serenity equally imperturbable. "Prodi-gi-ous!" was the only ejaculation they ever extorted from the much-enduring man.”