Oro comes from Rurouni Kenshin, the manga and anime series centred on Himura Kenshin, a former assassin trying to live peacefully in Meiji-era Japan. In the story, oro is Kenshin's habitual interjection whenever he feels flustered, surprised, or unsure how to respond, and it quickly became one of his most recognisable traits. Clips of the sound circulated among anime fans, then spread through reaction videos, edits, and soundboards, where its brevity made it easy to reuse. It remains popular because it instantly signals confusion without needing any dialogue or context.