* A typo or misspelling: Perhaps the intended phrase was something similar, but with a few letters changed.
* An acronym or abbreviation: Without context, it's difficult to guess what it could stand for.
* Slang or jargon: It might be a term specific to a particular group or community.
To understand the meaning, you need more information:
* Where did you encounter this phrase? Was it in a conversation, online, or in a written text?
* What was the context surrounding the phrase? What were the people talking about or what was the document about?
With more context, it might be possible to figure out what "t no plh" means.