Hopkins died at the age of 27 in 1647 from tuberculosis, but before his death he published an influential witch-finding manual titled The Discovery of Witches (1647). In the book he claims he got started in the witch-finding business because there were several women in his home town of Manningtree who were witches. Here (writing about himself in the third person) he explains what happened:
... In March 1644 he had some seven or eight of that horrible sect of Witches living in the Towne where he lived, a Towne in Essex called Maningtree, with divers other adjacent Witches of other towns, who every six weeks in the night (being alwayes on the Friday night) had their meeting close by his house and had their severall solemne sacrifices there offered to the Devill...
Hopkins goes on to write that he heard one of the witches calling out to her familiar spirits. Familiar spirits were allegedly magical entities that witches commanded to do their bidding. They often appeared in the form of animals, and many people believed they were demons loaned to witches by the Devil and that they nourished themselves by sucking the witches' blood.
|An illustration from The Discovery of Witches|
I don't think he's quite right. I think Hopkins or his associates actually did invent most of those names, but he didn't invent the name Pyewacket. That's the name of a Native American tribe that lived in New Hampshire and Maine in the 17th century. Matthew Hopkins never visited New England, but he probably did hear about the explorations of Darby Field.
Darby Field was an Irishman who came to New England in the 1630s and settled in New Hampshire around 1638. Many of the colonists were focused on work, family and God, but Field apparently had a more inquisitive spirit. Although he worked as a ferryman he could also speak the local Alonquin dialects and was interested in exploring the area around him. In 1642 he decided to climb the White Mountains and hired some local Native guides from a village called 'Pigwacket' to help him. Pigwacket was Field's rough English transcription of Pequawket, a name of one of the Abenaki groups that lived in New Hampshire and Maine.
Field's mountain-climbing expedition was well-known at the time and appears in both Massachusetts governor John Winthrop's journal and in a book by the explorer Ferdinando Gorges. It seems likely that Matthew Hopkins heard the name Pigwacket and incorporated it as "Pyewacket" into The Discovery of Witches. The Puritans erroneously believed that Native Americans worshipped the Devil so it makes that Hopkins would use a Native American word as a demon's name.
The Pequawket sadly no longer exist as a distinct group - they've merged with other Abenaki tribes - but the name Pyewacket continues on long after Hopkins's death. Pyewacket is the name of Kim Novak's cat in the movie Bell, Book and Candle (1958), has appeared as a character in several novels, and is the title of a recent horror film. I searched Tumblr and saw a lot of photos of animals named Pyewacket, while Instagram has over 7,000 posts with the hashtag #pyewacket. The dominant colonial culture's use of the word has outlived the actual indigenous people who inspired it.
I don't think Pyewacket's origins in New England (and in Puritan xenophobia) is well-known. I just stumbled on it recently in Emerson Baker's excellent book A Storm of Witchcraft: The Salem Trials and The American Experience (2015). There's always something new to learn about our region's weird history.