This is in fact a very rare song. The full plot is that a lady of Bristol (or London or Leimster) wants to marry Jimmy but her father does not consent. Her father has found another match for her. She tells her father that she loves Jimmy, and writes him a letter. The father tells the daughter to choose between Jimmy being sent away or being shot, and she says that she would rather see him sail away than be killed. The father is moved by her argument and consents to the marriage.
In the few collected versions come mainly from Canada, and apart from a Yorkshire version noted over 100 years ago, the Brazil’s family version is unique.