live off the fat of the land = live on the fat of the land
have the best of everything
In Genesis 45 : 18, Pharaoh tells Joseph's brothers : ye shall eat the fat of the land. Fat meaning the best part or choicest produce is now found only in this expression.
RELATED IDIOMS :
the fat is in the fire
something has been said or done that is about to cause trouble or anger
This expression refers to the sizzling and spitting caused by a spillage of cooking fat into an open flame. It was first used, in the mid 16th century, to indicate the complete failure of a plan or enterprise.