Come, come, dispatch: the Duke would be at dinner;
Make a short shrift: he longs to see your head.
Hastings:Richard The Third Act 3, scene 4, 94–97
O momentary grace of mortal men,
Which we more hunt for than the grace of God!
"Short shrift" is a darned confusing idiom. Some use "short shrift" as the equivalent of "quick work,' while others seem to mean "inadequate time." Both meanings indirectly stem from Shakespeare's. "Shrift" means "confession," from the verb "shrive"—a priest "shrives" someone by hearing confession and allotting a penance. (From "shrive" we also derive "Shrove Tuesday," or Mardi Gras, the day of merriment before Ash Wednesday confession and the beginning of Lent.)
To "make a short shrift," then, literally means to make a brief confession. We use the phrase very differently today: short shrift is now something you are "given" rather than something you "make" or perform. And to "give short shrift" is simply to allot small consideration to a person or idea; the notions of contrition and penance, once the essence of the phrase's irony, are now given short shrift.
As the bloody War of the Roses enters its final phase, Richard Duke of Gloucester rounds up everyone he deems an enemy, including his former accomplice Hastings. According to Richard's henchman Ratcliffe, Hastings's execution is holding up Richard's dinner. He advises the doomed Hastings to repent his sins as quickly as possible—to "make a short shrift"—so that his execution may proceed apace. Hastings suddenly realizes that Richard's courtesies to him were all manipulations, and that his own efforts to seek the grace of powerful men like Edward IV and Richard were doomed to fail. The grace of men is a sometime thing, determined by self-interest; only the grace of God endures.