What is the meaning behind the title of Steinbeck's East of Eden?
The title of John Steinbeck's East of Eden is an allusion to the Book of Genesis in the Bible. Genesis begins with the creation of the world and Adam and Eve's life in the Garden of Eden, a paradise of bliss and innocence. As you're no doubt aware, Adam and Eve sin and are thrown out of the garden. Following this experience, Eve gives birth to two sons, Cain and Abel, and Cain eventually murders Abel out of jealousy.
By making an explicit allusion to this classic Bible story, Steinbeck deliberately signals that he's going to parallel it. Adam and Cathy (later Kate) parallel Adam and Eve in some ways (often with a twist, especially in Cathy's case), while their sons, Cal and Aron, closely resemble Cain and Abel (also with a twist). Thus, Steinbeck turns his novel of the Trask family into an epic saga with moral and philosophical weight similar to the Bible's. Since the title of the book and the Biblical allusion in it is essential to signaling this intention, the title is a vital aspect of the book's central themes and meaning.