|Mormon 4:3 places the city Teancum on the borders by the seashore, close to the city Desolation. Because this city is not called the city of Teancum, I assume the city was not named after the man Teancum. I further assume they both derive their names from being built or born on the coast, which is what I believe the name Te-ancum means.
Once again I believe, "Te" means the end of. I have extrapolated the meaning of the term "ancum" from Ripliancum. When Coriantumr and Shiz were in their final battles, they came to the waters of Ripliancum, which Ether 15:8 describes as being "large or to exceed all."
Many Book of Mormon writers apply this term to the marshy lands of southern Mexico, currently known as the Papaloapan water basin. This area is indeed a large area of lakes, rivers, lagoons and swamp-land. But the Book of Mormon does not say the area they came to was a really big area of water. What it says is that the area of water they came to was, "large or to exceed all." There are many other places of water that are larger than the Papaloapan basin. It is not so large that it "exceeds all," not even close.
What is "large or to exceed all," is the ocean. I feel certain this is the meaning of the term Ripliancum. It is the equivalent of the Nephite term, Irreantum,
(see 1 Nephi 17:5)
Ripli-ancum in where the water all ends up, the ocean, which is "large or to exceed all."
And remember the person writing this record, had seen the whole history of this planet, every time period, every person, and every place. (see Ether 3:25 and Ether 4:4) Ether and Moroni both knew the ocean was the body of water that exceeded all, not a small water basin in southern Mexico.
Therefore if Ripliancum is where all the water ends up, I believe "ancum" refers to areas of waters that flow into the ocean. Te-ancum I believe means, the end of the rivers, where they spill into the ocean.
This is a protracted way of saying the City Teancum was on the coast, more than likely by the mouth of a river. This would also be where the man Teancum was from. The city was not named after him, both were named because of the geography of their setting and/or birth.