The abstract noun "song" can be expressed with the verb "sing." AT: "But now they sing songs about me to taunt me" (See: [[rc://en/ta/man/translate/figs-abstractnouns]])
Here "byword" is a metonym for the person about whom people make cruel jokes. AT: "I am now one whom they make cruel jokes about" or "They joke and say cruel things about me" (See: [[rc://en/ta/man/translate/figs-metonymy]])
A bow that is unstrung is not useful. The phrase "has unstrung the string of my bow" is a metaphor for making Job powerless. AT: "God has taken away my power to defend myself" (See: [[rc://en/ta/man/translate/figs-metaphor]])
A restraint keeps a person from moving freely and doing what he wants. Here "restraint" represents refraining from doing something, and "cast off restraint" represents not refraining from doing something. In this case the mockers did not refrain from being cruel to Job. AT: "do not refrain from being cruel to me" or "do whatever cruel things they want to do to me" (See: [[rc://en/ta/man/translate/figs-metaphor]] and [[rc://en/ta/man/translate/figs-explicit]])