Today is the Tuesday before Lent. In French, it’s Mardi Gras (“Fat Tuesday”); in English, we have the name Shrove Tuesday. (Also Pancake Day, from the custom of using up milk, eggs, and butter before Lent begins.)
Shrove Tuesday is the last day of Shrovetide, a period of about a week before Lent starts on Ash Wednesday. Shrove is a variation of the verb shrive; in the church, this means to hear the confession of and administer absolution to. From Romeo and Juliet [II, 4]:
[Romeo] Bid her devise
Some means to come to shrift this afternoon;
And there she shall at Friar Laurence’ cell
Be shrived and married.
Shrovetide is a time to be shrived (or shriven) so as to enter Lent in a state of grace. (Plus full of pancakes.)
As we see in Romeo’s dialogue, shrive also gives us the noun shrift for the act of absolution. This is still common in the phrase short shrift, which literally means a quick confession due to, um, circumstances, such as an executioner standing by. Shakespeare again, this time Richard III [III, 4]:
[Ratcliff] Dispatch, my lord; the duke would be at dinner:
Make a short shrift; he longs to see your head.
Our usage of short shrift has been bleached and broadened a bit, so we now just use it to mean doing something quickly and/or with insufficient attention.
Shrive, shrove, shrived/shriven, and [short] shrift all go back to Old English scrīfan. The Saxons used scrīfan to mean “impose penance”. But it also had a more general sense of “decree, ordain; assign”.
In Beowulf, Grendel is mortally wounded, but he manages to escape and retreat to his lair. Beowulf reports back to the king:
[…] þǣr ābīdan sceal
maga māne fāh miclan dōmes,
hū him scīr metod scrīfan wille
there must await,
the creature stained with crimes, the great judgement,
how him the bright Measurer of Fate wishes to decree
It’s clearer to pull out the relevant part: “hū metod him scrīfan wille”: how (what) the Lord for him will ordain.
You might guess that scrīfan is related to the German word schreiben, and you’d be right. In fact, versions of this word appear in all the Germanic languages, suggesting that this was a very early borrowing from Latin scrībere, meaning “to write”.
Although these days we use shrive rarely and primarily with religious meaning, we have a lot of its cousins still — words with scribe or script in them: describe, inscribe, subscribe, conscript, manuscript, postscript, superscript.
And although your doctor might not scrifþ (decree) you a particular medical regimen these days using an Old English term, he might prescribe you one.