The tongue is a metonym for what people say. James calls it a fire because of the great damage it can do. Alternate translation: "The tongue is like a fire" (See: [[rc://en/ta/man/translate/figs-metonymy]] and [[rc://en/ta/man/translate/figs-metaphor]])
The tongue here is a metonym for the words of the person whose tongue it is, and the body is a synecdoche for the whole person. The words defiling the person is a metaphor for God rejecting a person who speaks evil words. (See: [[rc://en/ta/man/translate/figs-metonymy]] and [[rc://en/ta/man/translate/figs-synecdoche]] and [[rc://en/ta/man/translate/figs-metaphor]])
The phrase "course of life" refers to a person's entire life. Alternate translation: "it ruins a person's entire life" (See: [[rc://en/ta/man/translate/figs-metaphor]])
The word "itself" refers to the tongue. Also, here "hell" refers to the powers of evil or to the devil. This can be stated in active form. Alternate translation: "life because the devil uses it for evil" (See: [[rc://en/ta/man/translate/figs-activepassive]] and [[rc://en/ta/man/translate/figs-metaphor]])