"shrift, shriving," 1570s, shortened from Shrovetide (early 15c.), from schrof-, related to schrifen (see shrive). Shrove Tuesday (c.1500) is from practice of celebration and merrymaking before going to confession at the beginning of Lent.
Old English scrifan "assign, prescribe, ordain, decree; impose penance, hear confession; have regard for, care for," apparently originally "to write" (strong, past tense scraf, past participle scrifen), from West Germanic *skriban (cf. Old Saxon scriban, Old Frisian skriva "write; impose penance;" Old Dutch scrivan, Dutch schrijven, German schreiben "to write, draw, paint;" Danish skrifte "confess"), an early borrowing from Latin scribere "to write" (see script (n.)), which in Old English and Scandinavian developed further to "confess, hear confession."