I used to think that being shriven was something a Jewish boy endured at a bris. But in fact, if the word belongs under any religious umbrella it would have to be Catholicism. Being shriven involves giving one's confession, as to a priest, and has at different times through history focused on confession, penitence, or absolution. Shrift as a synonymous noun for confession is used in Romeo and Juliet when Romeo details a plan to the Nurse.
Bid her devise
Some means to come to shrift this afternoon;
And there she shall at Friar Laurence' cell
Be shrived and married.
(Act II Scene IV)
Shrift comes to us from the Old English scrift which, along with shrive, shriven, etcetera, is derived from the Latin scribere meaning to write. However, shrive was never used as a direct replacement for write, and instead was used as decree or impose penance in both Old English and Scandinavian languages.a
As is usually the case, short shrift is first documented in use by Shakespeare. In Richard III, Ratcliff addresses Lord Hastings after Richard condemns him to death.
Dispatch, my lord; the duke would be at dinner:
Make a short shrift, he longs to see your head.
(Act III Scene IV)
Here, Richard wishes for a short confession so that the main event, the execution, can be carried out forthwith. Lord Hastings is given short shrift.
It is not until 1814 that the phrase is documented again in Sir Walter Scott’s, The Lord of the Isles.b It cannot be proven, but Scott most likely borrowed the phrase directly from Shakespeare, and his popularity at the time influenced the modern usage of the idiom, if in a different form. Today, giving someone short shrift means to pay them little attention; as to an unimportant or trifling matter.c
Now that you are aware of the history, the next time someone is bothering you incessantly about an unimportant matter, you can give them short shrift; quickly take their confession, and send them off to the gallows. At least... in your own mind, of course.d
kthejoker says: etymologically speaking, there's also describere, which while meaning "from the written", was their shorthand way of implying an oral account of something... when talking about an oral account or recollection, they would use describere rather than scribere.
See more phrases Shakespeare invented
a Shrift actually comes from the perfect passive participle of scribere; in Latin, what is prescribed.
b "Short were his shrift in that debate. If Lorn encounter'd Bruce!"
c An example in usage: "Every argument...tells with still greater force against the present measure, and it is to be hoped that the House of Commons will give it short shrift to-night." (1887 The Times of London)
d The Tuesday before Ash Wednesday (you know, Mardi Gras?) is traditionally referred to as Shrove Tuesday in the UK and Australia.