Nyanpassu comes from Non Non Biyori, a slice-of-life anime that began in 2013, where first-grader Renge Miyauchi uses it as her own cheerful greeting. The word caught on because it sounds like a cat's meow mixed with a friendly hello, and fans began quoting it in comments, fan art and short clips. As the series gained a wider audience through streaming and social media, the greeting became a shorthand for Renge's innocent personality and for the show's gentle rural humour, keeping it popular in anime edits years later.