* A misspelling: Perhaps it's intended to be "Did You Know That" or a similar phrase.
* A specific term: It could be used within a particular community or field that you're not familiar with.
* A made-up term: It could be a unique slang term or inside joke.
To figure out the meaning, you'd need more context. For example:
* Where did you see it used?
* Who used it?
* What was the overall topic or conversation?
Providing more information will help me understand what "DYKTW" means.