Prepare for a joyful occasion or a warm welcome. For example, When Bill comes home from his trip to Korea we're going to kill the fatted calf. This expression alludes to the parable of the prodigal son (Luke 15:11–32), whose father welcomed him by serving the choicest calf after his return. [Early 1600s]
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.