1560s, in reference to diseases, "virulent, tending to produce death," from French malignant and directly from Late Latin malignantem (nominative malignans) "acting from malice," present participle of malignare "injure maliciously," from Latin malignus "wicked, bad-natured," from male "badly" (see mal-) + -gnus "born," from gignere "to bear, beget" (from PIE root *gene- "give birth, beget").
Earlier in the church malignant "followers of the antichrist," from Latin ecclesiam malignantum in early Church writing, applied by Protestant writers to the Church in Rome (1540s). Of persons, "disposed to inflict suffering or cause distress," from 1590s. As an adjective, Middle English used simple malign (early 14c.), also malignous "poisonous, noxious." Related: Malignantly.
c. 1600, "malignant nature;" 1650s, "state of extreme malevolence, bitter enmity," from malignant + abstract noun suffix -cy. Of diseases, growths, tumors, etc., "virulence, tendency to get worse," from 1680s. In English history, "adherence to the royal party in the time of Cromwell," 1640s, from malignants, a term applied to the royalists by their enemies.
"increase the bitterness or virulence of, make (a feeling, a conflict, etc.) more hostile or malignant," 1650s, a back-formation from exacerbation or else from Latin exacerbatus, past participle of exacerbare "irritate, provoke." Related: Exacerbated; exacerbating.
Middle English cursen, from Old English cursian, "to wish evil to; to excommunicate," from the source of curse (n.). Intransitive meaning "swear profanely, use blasphemous or profane language" is from early 13c. (compare swear (v.)). The sense of "blight with malignant evils" is from 1590s. Related: Cursed; cursing.