The answer is: “These old bones live to learn her wanton ways:”
Metonymy occurs when an idea is referred to by the name of something closely associated with it.
In the poem "I Knew a Woman," the author Theodore Roethke directs attention to his lover and is determined to give in anything for her. In that respect, he makes use of the phrase "old bones" to mean that his own body will live for her naughty behavior.