The title has great significance, it foreshadows some of the important themes of Hemingway's novella, The Old Man and the Sea. In addition, the title focuses our attention on the central relationship in the story, that between the old man, Santiago, and the sea, including the mighty and terrible creatures that live therein. The title tells us that while Santiago's relationship to Manolin is important and the embodiment of the themes of love and youth versus old age, it is not the central relationship in the story.
One theme the title foreshadows is that of the human condition. Hemingway explores the struggle of humankind to survive in an environment that is fierce and forever needs subduing. For a lifetime, Santiago has gone out onto the mighty sea to wrestle livelihood from it by simultaneously understanding and working in harmony with its ways and overpowering it and conquering its ways. It is the old man in a contest with the sea--especially the contest with the marlin that Hemingway tells of--that embodies the human condition of struggle and harmony with and in our environment.
He was an old man who fished alone in a skiff in the Gulf Stream and he had gone eighty-four days now without taking a fish. ... Everything about him was old except his eyes and they were the same color as the .sea and were cheerful and undefeated.
the title is already a theory that introduces a struggle between and old man that means ( weakness , and wisedom ) and the sea ( the power and strong )