The lyrics of "I'm Shipping up to Boston" by Dropkick Murphys tell the story of a sailor who has lost his leg during the climb of the rigging. He refers to himself as a "sailor peg" which could be interpreted as him being replaceable by any other sailor, just as a peg can easily be replaced. The repetition of the first verse emphasizes his physical loss and the difficulty he had in performing his job as a sailor due to the loss of his leg.

The chorus of the song serves as a call to action and an expression of the sailor's determination to continue living a seafaring life despite his disability. He's shipping off to Boston to find his wooden leg, which symbolizes his desire to regain a sense of normalcy and independence. The use of the word "shipping" further emphasizes his identity as a sailor and his need to continue in his chosen profession.

The song is a powerful tribute to the resilience and perseverance of seafarers, who face unimaginable challenges and dangers in their line of work. It also highlights the strength of the human spirit and the ability to overcome adversity and continue on with one's goals and aspirations.