1590s, of persons, "free from passions, calm, disposed;" 1640s, "not dictated by passion, impartial;" from dis- "the opposite of" + passionate. Related: Dispassionately.

c. 1300, from Old French ire "anger, wrath, violence" (11c.), from Latin ira "anger, wrath, rage, passion," from PIE root *eis- (1), forming various words denoting passion (source also of Greek hieros "filled with the divine, holy," oistros "gadfly," originally "thing causing madness;" Sanskrit esati "drives on," yasati "boils;" Avestan aesma "anger;" Lithuanian aistra "violent passion").

Old English irre in a similar sense is unrelated; it is from an adjective irre "wandering, straying, angry," which is cognate with Old Saxon irri "angry," Old High German irri "wandering, deranged," also "angry;" Gothic airzeis "astray," and Latin errare "wander, go astray, angry" (see err (v.)).

"heat of passion or desire," mid-15c., from Old French ardure "heat, glow; inflammation; passion" (12c., Modern French ardeur), from Latin ardorem (nominative ardor) "a flame, fire, burning, heat;" also of feelings, etc., "eagerness, zeal," from ardere "to burn," from PIE root *as- "to burn, glow." In Middle English used of base passions; since Milton's time of noble ones.

late 14c., "insanity, lunacy, dementia; rash or irrational conduct, headstrong passion, extreme folly," from mad (adj.) + -ness. Sense of "foolishness" is from early 15c.

especially of animals, "desire copulation, be under the influence of sexual passion," late 14c., ruteien, from rutei, probably an Anglo-French form of the noun (see rut (n.2)). Related: Rutted; rutting.

"passiveness," 1650s, from passive + -ity. Middle English had passion in a sense of "fact or condition of being acted upon" (c. 1400), also passabilite "capacity for being acted upon or suffering" (mid-14c.; see passible).

"temper, anger, passion," 1831, American English, of unknown origin; perhaps a figurative use somehow of dander (n.1), or of West Indian dander, dunder "fermentation of sugar" (in English from 1796), from Spanish redundar "to overflow," from Latin redundare (see redundant).

1570s, "without haste or passion," from cool (adj.) + -ly (2). From 1610s as "without heat;" 1620s as "in an indifferent manner;" 1844 as "with quiet presumption or impudence."