Pennacook - A tribe of northeastern Indians, related to the Abnaki, who lived in parts of new Hampshire, Massachusetts, and Maine. They were also known as the Merrimac, from the river of that name. Some still live in Maine with what are known as the St. Francis Indians, remnants of many New England tribes. The town of Penacook and Lake Penacook, both in Merrimack County, New Hampshire, are named for them, as is a branch station of the Concord post office. Their name also appears in Whittier's poem The Bridal of Pennacook