If you actually have a file with this name and want to see what's inside:
: Do not open unknown .mp4 files from untrusted sources, as they can sometimes be disguised executables or contain exploits.
Given the cryptic nature of the string, it fits the profile of or ARGs (Alternate Reality Games). These genres often use "found" file names to create a sense of unease or nostalgia for the early internet era. If you were to create a story around this, it might involve:
If "TKUNDmp4" is a personal project or a niche file you've discovered, you might be looking for information on how to handle it or a creative interpretation of its potential mystery. Analysis of the Components