The sound comes from Fate Grand Order, the mobile role playing game first released in Japan in 2015, where Leonardo Da Vinci appears as a Servant. Fans call her younger Rider form Da Vinci Lily, or Loli Vinci, and clipped her repeated humu humu line from voice lines shared online. As Fate edits spread across video platforms, the tiny clip became a standalone reaction on soundboards, kept alive because its smug, thoughtful tone fits far beyond its original game context.