The only time most modern Christians refer to the Harrowing of Hell is when they recite the Apostles' Creed: "and descended into Hell," where Christ was believed to have wrested the souls of good people such as Abraham and Isaac from the clutches of the devil on Holy Saturday and released them to Heaven. (Calvin called this a childish fable, by the way, and most Catholics just don't mention it anymore.)
We talk about having a harrowing day, and presumably the Prince of Darkness would have had one of those on that first Holy Saturday. In a Middle English play from the Towneley or Wakefield Cycle called "The Deliverance of Souls," the first response of a demon called Ribald to the appearance of Christ in the underworld is:
Sen fyrst that hell was mayde / And I was put therin,
Sich sorow neuer ere I had, / nor hard I sich a dyn;
My hart begynnys to brade / my wytt waxys thyn,
I drede we can not be glad / thise saules mon fro vs twyn.
how, belsabub! bynde thise boys, / sich harow was neuer hard in hell.
Since hell was first made and I was put therein
Such sorrow never have I had, nor heard I such a din.
My courage begins to weaken, my wits wax thin
I fear we cannot be glad, these souls will be taken from us
Bind these boys, Beelzebub! Such "harrow" never was heard in Hell.
And later he cries, "out, harro, out!" And Satan exclaims:
Besegyd aboute! whi, who durst be so bold,
for drede to make on vs a fray?
Besieged about! Why who dares be so bold to attack us?
If your Middle English is up to the challenge, you can read the whole play here. Or you can download James Halliwell's 1840 translation of the Middle English "The Harrowing of Hell" (with the original on facing pages) here.
But what does it mean "to harrow"?
Harrow comes from Old English hergian, the same root as the word harry. According to the Online Etymological Dictionary, hergian meant to "make war, lay waste, ravage, plunder, [it was] the word used in the Anglo-Saxon Chronicle for what the Vikings did to England." In other words, harrow means to rip loose and tear things up, although artistic and poetic renderings of the Holy Saturday harrowing tend to take a rather more distinguished tone. In the noun form it also refers to a type of plow which "rips up" the ground, and in verb form it means "plowing up."