It's a local term for a wetland. According to the always correct Wikipedia, it's originally a Cree word. It is not as cool-sounding as reedswamp, mire, fen, or vlei. All wetland terms sound Jabberwoky'd to the maxx. I love it. This is a muskeg:
This is what we scientists call a "country muskeg." They're kind of everywhere and boring. Although they are the primary habitat for little carnivorous Sundews (Drosera rotundifolia) and Butterworts (Picguicula vulgaris).
(Sundews on a sphagnum blanket bog)
In a marginally productive muskeg you get white bog orchids (Platanthera dilatata).
These smell like cinnamon and jasmine. They can grow to immense sizes in the right circumstances:
That orchid is about 3.5 feet tall. It is the symptom of an incredibly productive estuarine wetland system. That's me with my huge-ass gun I'm required to carry. (It's a Winchester .375 H&H for all of you that care. I shoot nossler (?) bullets. They come in a box that says Safari and has a silhouette of a rhino on it, so I'm cool.)
Higher quality muskegs get called fens around here. Fen is science for get's groundwater flow. Impress your parents with the word minerotrophic which means the same thing. This is by far my most favorite fen ever. It's in Game Creek, at the foot of a limestone complex called the Vortex on Chichagof Island.
O/T: the Vortex is/was also the name of a lime-green roller coaster at Great America, in the Bay Area. I think it's now called Paramount's Great America or Gillette presents Pac Bell's interpretation of Paramount's Great American Expensive Day in Line. So, that's what I think of when I gaze at the majesty of the Vortex. (We are all looking at it in that picture, but I don't have a picture. sorry)
This is a calcareous fen--the richest and most productive wetland around here. They are just neat.
Now, I shouldn't have to explain what a Harpy is. tDF calls it yappy.