The proverb “revenge is a dish best served cold” traces to French (“La vengeance se mange froide”), appearing in English literature by the 19th century. Most Americans do not know the French orign of the proverb… It entered popular culture thanks to Star Trek. In Star Trek II: The Wrath of Khan (1982), Khan Noonien Singh delivers the line during a tense video call with Admiral Kirk:
Ah, Kirk, my old friend… do you know the Klingon proverb? ‘Revenge is a dish best served cold.’ And it is very cold… in space.