Literally: "to provide with force". Originally a localism from Northern China, meaning "energetic, forceful; exciting, interesting". Allegedly popularized by a viral fandub video of an episode from the Japanese anime Gag Manga Biyori (ギャグマンガ日和). In the episode "Saiyūki: The end of the journey" (西遊記 〜旅の終わり〜, Saiyūki: tabi no owari), one peculiar line was "这就是天竺么？不给力啊老湿！" ("This is India? This is not exciting at all, teacher."), uttered by Sun Wukong after discovering that, in the supposedly sacred place of Tianzhu (天竺, "an ancient name for India") they had arrived at, there was only a small streamer with the two characters "天竺" written on it.
Etymology from other Chinese dialects, for example Min Nan "kik-làt" ("to exert oneself") or Hainan Lingao dialect 给力 ("to provide with force, to beat"), may also be possible.
给力 (simplified, Pinyin 給力), traditional