It's not a city in Connecticut! The word means "Welcome" in Mohegan, and is printed at the top of the obverse of the Mohegan Sun $1 chip. The casino is located in Uncasville, CT.
This may seem obvious to you, but if you search the web for Wigwomun, you'll find a lot of non-us language sites that assume Wigwomun is the city the casino is. Not a bad assumption, just wrong.
What I've accomplished by posting this here is less clear.
I think I'll start answering the phone, "Wigwomun!" although it sounds a bit too much like Wig Woman.
I'll shut up now.
Jeff Wagg R-5774