be-all and end-all, the

The most important element or purpose, as in Buying a house became the be-all and end-all for the newlyweds. Shakespeare used this idiom in Macbeth (1:6), where Macbeth muses that “this blow might be the be-all and the end-all” for his replacing Duncan as king. [Late 1500s]

The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.