The phrase comes from Taiwanese Hokkien influenced slang used in Taiwan, where san xiao is a casual, slightly rude way to ask what on earth someone is talking about. Short spoken clips of everyday slang like this spread easily through messaging apps, livestream chats and short video edits because the meaning is clear even from tone alone. San Xiao La stayed popular as a compact reaction for moments of disbelief, especially among Mandarin and Hokkien speakers sharing memes, gaming clips and everyday frustrations online with friends and followers alike.