"Mahantongo" is a Lenape

Lenape

The Lenape are an Algonquian group of Native Americans of the Northeastern Woodlands. They are also called Delaware Indians. As a result of the American Revolutionary War and later Indian removals from the eastern United States, today the main groups live in Canada, where they are enrolled in the...

 word, translated "where we had plenty of meat to eat" or "good hunting grounds." The name is shared by a creek, a valley, and a mountain in central Pennsylvania

Pennsylvania

The Commonwealth of Pennsylvania is a U.S. state that is located in the Northeastern and Mid-Atlantic regions of the United States. The state borders Delaware and Maryland to the south, West Virginia to the southwest, Ohio to the west, New York and Ontario, Canada, to the north, and New Jersey to...

, and is a common street name in the area. The alternate spelling "Mahantango" is often found in early publications, e.g., (Floyd 1911).
The Mahantongo culture area is much more extensive than the creek valley itself.