Jesus is a figure who is of course immensely important in this novel, and in many ways the life stories of the other characters are based around the way that meeting Jesus impacts them and changes their lives, setting them on a new direction. Jesus is a figure who is named after his function in the society of which he is a part. He spends lots of time speaking in public places and teaching the people that surround him, including his disciples. As such, he is referred to as "the Teacher" by the public and the fishermen.
This name clearly recognises his status as a man of some wisdom and learning and also identifies his purpose as somebody who has come to teach and share that learning with others. It is part of his desire to teach those that listen to him and to see them learn more about God and his love for them, and the name that he is given reflects this aspect of the ministry of Jesus.