Arigatou is simply the Japanese word for thank you, so many online uploads use short clips of it without a clearly traceable single source. On soundboards and meme pages, it spread as a quick anime-flavored reaction that fits edits, chat replies and wholesome punchlines. Its staying power comes from how easy it is to understand even for non-Japanese speakers and how well it pairs with other short anime voice clips like Tuturu or Onii-chan in playful montage edits.