Some Griceian may contest that there's nothing 'good' (etymologically) about Good Friday. Since in "good bye", "good" is a corruption of 'God', could this be "God's Friday"?
Good Friday, n., formed within English, by compounding. Etymons: "good", adj. (compare "good" adj. 14c) + "Friday", n.
Good Friday is the Friday before Easter Sunday, on which the Crucifixion of Christ is commemorated in the Christian Church, traditionally observed as a day of fasting and penance.
1300 St. John Evangelist (Laud) 27 in C. Horstmann Early S.-Eng. Legendary (1887) 403
A-morewe, ase on þe guode friday, ase he deide on þe rode.
1300 St. Brendan (Laud) l. 366 in C. Horstmann Early S.-Eng. Legendary (1887) 229
Þare heo gounnen bi-leue A-gode friday al þe longue day for-to an ester eue.
1325) Cursor Mundi (Vesp.) l. 17288 + 81
Vse we ay After heghe ful of þe moyne to take þe next friday,
And þat hald we our gode friday.
1400) Mandeville's Trav. (Titus C.xvi) (1919) 50
Þere is a lampe þat hongeth before the Sepulcre..and; on the gode Fryday it goth out be himself.
1429 Mirour Mans Saluacioune (1986) l. 2947
Thus myght doelfulle Marye say on the Gude Fridaye.
1532 T. More, "Confut. Tyndale", in Wks. 651/2
The .iii. golden frydayes, that is to wit, the frydaye nexte after Palme sundaye, and the frydaye next afore easter day, and good fryday.
1579 Spenser. "Shepheardes Cal." Feb. 30
So semest thou like good fryday to frowne.
1635 F. Quarles Emblemes v. vii,
Chear up, my soul..and bear
One bad good-friday, full mouth'd easter's near.
1662 A. Conway Let. 24 May in Conway Lett. (1992) iv. 224
Since good fryday I have not been able to goe abroad.
1738 H. Taylor Let. 19 Sept. in T. Secker Corr. (1991) 18,
I shall officiate on Xtmas day and; Good Fryday according to Your Lordships directions.
1791 J. Boswell, "Life Johnson," anno 1783 II. 444
On April 18, (being Good-Friday,) I found him..drinking tea without milk, and eating a cross-bun to prevent faintness.
1837 Times 24 Feb. 2/5
On last Holy Thursday or Good Friday they were at the bakehouse of the Sieur Montonnet to heat the oven.
1859 G. A. Sala Twice round Clock (1861) 80
What becomes of all the cold crossbuns after Good Friday?
1868 W. M. Campion and W. J. Beaumont Prayer-bk. Interleaved (1876) 115
The term Good Friday is peculiar to the English Church.
1928 Public Opinion 6 Apr. 325/1
The newspapers do not publish on Good Friday.
1991 J. Trollope Rector's Wife vii. 87
The three-hour service on Good Friday, when Peter liked the church quite unadorned, with the crucifix above the altar shrouded in black.
2010 Leicester Mercury (Nexis) 7 Apr. 15
It is Good Friday and that is a Bank Holiday.
General attrib., as Good Friday mass, Good Friday service, etc.
1491 Mirk's Festialis (Caxton) sig. eiijv,
Our lorde Ihesu crist, that suffred for vs & all mankynde on good friday passion.
1563 Bp. J. Pilkington Burnynge of Paules Church sig. C.viiiv,
Good fridaye masse.
1595 A. Copley Wits Fittes & Fancies iii. 93
A Preacher in his good-friday sermon.
1663 J. Carleton Ultimum Vale 26
On Good-fryday night, she would not go to Bed, she said, but be at her Devotion.
1753 J. White. "Protestant Englishman" iv. §4. 285
If it was not consider'd as an Object of divine Adoration, what means the Good-Friday Service, and all the Ceremonies thereof.
1819 Scott Ivanhoe II. vii. 104
"Like a village girl at her first confession upon Good Friday eve."
1890 Dublin Rev. July 81
"All of these are represented in the Good Friday Mass."
1956 Life 2 Apr. 112/2 (caption)
"Good Friday communion for the congregation, long forbidden, is prepared by Rev. Ellis Wulfers carrying Blessed Sacrament under an umbrallino."
1961 J. Toland But not in Shame v. xx. 316
"Dirty clouds of smoke still rose to the left where woods were smoldering from the cataclysmic Good Friday bombardment."
1992 St. Louis Post-Dispatch (Nexis) 16 Apr. 3 a,
"Christ Church Cathedral (Episcopal), 1210 Locust Street, will have Good Friday services at noon and 12:30 p.m."
2011 Liverpool Echo (Nexis) 21 Apr. 70
"Evans will go straight into the Centurions squad for the club's Good Friday fixture with Barrow."
attrib., designating cakes, buns, etc., traditionally baked and eaten on Good Friday, esp. hot cross buns. Chiefly in Good Friday bun. Now rare.Traditionally some buns were baked until dry, hung up, and grated for medicinal use throughout the year.
1623 G. Markham Countrey Contentments, or Eng. Huswife (new ed.) vi. 223
Of these Gerts are made the good Friday pudding.
1654 E. Gayton Pleasant Notes Don Quixot i. v. 17
A piece of the groaning Cake, (as they call it) which she kept religiously, with her Good Friday Bun, full forty good yeares.
1753 Trial W. Smith in J. Blackburne Reg. Ingleby (1889) p. xxviii,
Mixing Arsenick in a Good-Friday Cake.
1825 W. Hone Every-day Bk. (1826) I. 202/2
In the houses of some ignorant people, a Good Friday bun is still kept ‘for luck’, and sometimes there hangs from the ceiling a hard biscuit-like cake of open crow-work, baked on a Good Friday, to remain there till displaced on the next Good Friday by one of similar make.
1876 F. K. Robinson Gloss. Words Whitby Pref. p. xii,
Best flour biscuits are made on Good Friday, to be kept as a year's supply for grating into milk or brandy and water to cure the diarrhœa; and with holes in the centre, we have seen ‘Good Friday biscuits’ hanging from the ceiling.
1905 B. Capes Jay of Italy iii. 27
He was none the less savage against circumstances—vicious, desperate, insolent with his master, as cross all over as a Good Friday bun.
1945 Strand Mag. Apr. 96 (crossword clue)
A Good Friday cake that some hang up as a charm against evil (3, 5, 3) [= hot cross bun].
Good Friday agreement n. Polit. an agreement between the British and Irish governments and the main political parties of Northern Ireland, setting out proposals for the securing of peace in Northern Ireland, including provisions for the formation of new political assemblies and commitments regarding such issues as the release of prisoners and the decommissioning of the weapons of paramilitary organizations.
The agreement was reached at Stormont Castle, Belfast, on Good Friday (10 April) 1998, and its terms passed by public referendums in Northern Ireland and the Republic of Ireland on 22 May 1998.
1998 Belfast News Let. (Nexis) 31 Mar. Confidently forecasting a Good Friday agreement, he [sc. Senator George Mitchell] said: ‘I think I have enough experience to judge when something is realistic.’
1998 Press Jrnl. (Vero Beach, Florida) 11 Apr. a15 President Clinton called the Good Friday agreement ‘the best chance for peace in a generation.’
2001 B. Ahern in Herald (Glasgow) (Electronic ed.) 2 Feb. These are issues that are extremely important for the peace and security of everybody in Ireland and to see the full implementation of the Good Friday Agreement.
2010 Church Times 10 Sept. 13/3 Since the Good Friday Agreement, increasing numbers of Roman Catholics serve in the Police Service of Northern Ireland.
'good', designating a day on which or season in which religious observance takes place. Chiefly in Christian contexts (usu. in Good Friday n.); in later use also occas. in Jewish contexts (cf. yom tov n.).
With reference to Jewish religious holidays, after Yiddish yontev and its etymon biblical Hebrew yōm ṭōḇ yom tov n.
good tide: see good tide n. Good Wednesday: see Special uses 3.
OE Confessor's Exhort. to Penitence (Corpus Cambr. 190) in B. Thorpe Anc. Laws & Instit. of Eng. (1840) II. 224
Ðeos tid cymð ymbe twelfmonað þæt ælc man sceal his scrift gesprecan...
Þonne hafa þu rihtne geleafan to Gode and; to þysse godan tide.
1500 in C. Brown Relig. Lyrics 15th Cent. (1939) 123 (MED),
Thre kyngys come on goid xij day.
1620 Hist. Frier Rush sig. B2v,
Vpon a good night, all the whole Convent assembled together in the Quier.
1654 J. Trapp Comm. Minor Prophets ii. 35
She shall neither have holy-dayes nor good dayes (as they are called, Esth. 8.17.) to keep and celebrate.
1723 J. Barker Patch-work Screen for Ladies ii. 45
When Duty and good Days call'd me to Church, I thought I might find there some Compeeresses, or Persons of my own Stamp.
1886 Sabbath Visitor 421/1 Nov.
These three festivals or feasts are called good days or holidays, because they are set aside more for rejoicing than for deep thought.
1902 Menorah Mar. 177
He remembers his childhood days, the Jewish ‘good-days’, Sabbaths, the illuminated synagogue, [etc.].
2000 N. Kanellos Noche Buena 83
Christmas Eve, the Good Eve, was the time for the patriarchal feast at the Olivareño.