He was respected by his people as a warrior and a leader, and his name can be translated as "the New Moon", due to his habits of taking long walks by the moonlight. His tribe caught fish, dug shellfish and raised corn on the Marblehead peninsula.
His band of Massachusett people were known as the Naumkeag, and they resided in the area now occupied by Marblehead, Salem, Lynn, Saugus, Revere and Medford. In 1617, he sent a war party of Massachusett warriors to aid the Penobscot tribe in their conflict with the Tarratines of northern Maine.
The Tarratines were a warlike band, who did not practice agriculture and who supplemented the food supplies that were not obtained by hunting with raids on the stores of bands who resided along the New England coast and its tidal rivers. They sent war parties to avenge the support of Nanepashemet for their Penobscot enemies. Sensing danger, Nanpashemet built a log fort near the Mystic River in present-day Medford. He directed his wife and children to move inland to reside with friendly Indian bands until the crisis passed.
In 1618, an epidemic of smallpox decimated his band, but he was spared because of his isolation in the fort. By 1619, the Tarratines discovered his whereabouts, laid siege to the fort and ultimately killed Nanepashemet.
His wife, who is only known as the "Squaw Sachem" ,and whose real name remains unknown, ruled his lands aggressively and capably after his death. She befriended the English Puritans and divided her lands among the three sons of Nanepashemet. She died in 1650 and is purported to be buried in an unmarked site in the present day City of Arlington, Massachusetts.