Many online tools use the original source's ID as the filename.
Apps like TikTok or Instagram often assign strings of numbers to video exports.
When you see a name like this, it is usually the result of your operating system's feature.
If you are looking for a that was titled this way, let me know: Where did you find or download it? What was the content of the video? How long is the video? 3399 (Bad output framerate decision for mp4 from camera)