ハイテンション

1847 is Merriam-Webster's first-known-use point for English high-tension in the sense of high voltage. The parts are English high and tension, but Japanese ハイテンション is not a direct English phrase for mood. Japanese already had テンション by 1894, when Seisenban Nihon Kokugo Daijiten cites Natsume Soseki's letter to Masaoka Shiki with テンション. In postwar and late Showa entertainment talk, テンション changed from mental strain and physical tension to 気分 or mood. Digital Daijisen treats that mood sense as a popular extension, and ハイテンション became a Japanese-built compound beside ローテンション and テンションが上がる. The opposite ローテンション is also listed in Japanese dictionaries as its pair. Youth TV, comedy, and variety shows associated it with visible excitement rather than stress. Today ハイテンション describes a person, room, or performance with unusually high energy: 朝からハイテンションだね. In English, high-tension usually refers to cables, batteries, stress, or conflict, not cheerful behavior. Cambridge labels high-tension as old-fashioned for high-voltage, and Merriam-Webster defines it as using high voltage. Natural English choices are hyper, excited, energetic, or in high spirits.