If you have more context, like where you found this file or a description of what's in it, I might be able to help you track down the original creator or more details.
This naming convention—a long hexadecimal string followed by "_source"—is typically used for internal file management by content delivery networks (CDNs), social media platforms (like Reddit or Discord), or cloud storage services to index uploaded content. 5f3ed947c2cec8e55655e_source.mp4