The term "1337" is a stylized version of the word "elite," part of a dialect called "leetspeak" used by early hackers and online communities. The "b" prefix is often used in file naming conventions or as a shorthand (such as for "build" or "beta").
While there is no single widely recognized "b1337.mp4" viral video or media artifact, the name is a specific combination of two prominent internet culture elements: "1337" (leetspeak) and the MP4 video format. Analysis of "b1337.mp4" b1337.mp4
If you encountered this specific filename, it likely falls into one of these three categories: What is MP4 File Format The term "1337" is a stylized version of