Entalassen is a German word referring to the term to release something.
The document by William Bradford, where he tells the story about john Howland was a journal of his life, where Bradford describes the story of the Pilgrims from 1608.
The chapter begins with Bradford referring to the resolution of some troubles. The boat the Separatists had set out from England on, the Speedwell, had developed leaks, so the passengers transferred to the Mayflower, which was a cargo ship. This was uncomfortable fit for the people on board.
the intention of the author was to show everyone the life conditions Pilgrims had at that time, feel free to take advantage of that to explain and deep dive in the intention of the book.
From what I could find, Sirens are asking for help. The song they sing is a cry for help. They are described as acting/singing like a "damsels in distress".