perturbed (adj.)

late 14c., perturben, "disturb greatly, disturb mentally; cause disorder in," from Old French perturber "disturb, confuse" (14c.) and directly from Latin perturbare "to confuse, disorder, disturb," especially of states of the mind, from per "through" (from PIE root *per- (1) "forward," hence "through") + turbare "disturb, confuse," from turba "turmoil, crowd" (see turbid). Related: Perturbed; perturbing.

1721, from assimilated form of in- (1) "not" + perturbed. Related: Imperturbedly.