Here's why it's unlikely to be a standard term:
* "Marsh" refers to a type of wetland, while "wort" is an old word meaning "plant" or "herb." So, the combination technically means "marsh plant."
* Many plants grow in marshes, but "marshwort" doesn't specify which one.
* There's no official scientific name for a plant called "marshwort."
Possible explanations for its use:
* Local dialect: It could be a local name for a specific plant in a particular region.
* Misunderstanding: It could be a mishearing or misspelling of another plant name.
* Informal use: Someone might use it to describe any plant found in a marsh, similar to how people might use "wildflowers" to refer to any blooming plant in the wild.
To understand the origin of "marshwort" more clearly, it's helpful to know:
* Where did you hear this word used?
* What context was it used in?
* What was the speaker referring to?
With more information, we can better understand what "marshwort" might mean in your case.