The phrase comes from everyday Japanese as heard in anime dialogue, where eh expresses surprise and sonna suggests something like such a thing or no way. Clips built around short, expressive Japanese lines like this spread through meme pages and soundboards because they work even for listeners who do not speak the language. Editors reuse the moment as a universal shocked reaction, similar in spirit to an oh my god meme, pairing it with subtitles, captions and exaggerated facial expressions to make the disbelief instantly clear.