the Friday before Easter, c. 1300, from good (adj.) in Middle English sense of "holy, sacred," especially of holy days or seasons observed by the church; the word also was applied to Christmas and Shrove Tuesday. Good Twelfthe Dai (c. 1500) was Epiphany (the twelfth day after Christmas).
Old English gōd (with a long "o") "excellent, fine; valuable; desirable, favorable, beneficial; full, entire, complete;" of abstractions, actions, etc., "beneficial, effective; righteous, pious;" of persons or souls, "righteous, pious, virtuous;" probably originally "having the right or desirable quality," from Proto-Germanic *gōda- "fitting, suitable" (source also of Old Frisian god, Old Saxon gōd, Old Norse goðr, Middle Dutch goed, Dutch goed, Old High German guot, German gut, Gothic goþs). A word of uncertain etymology, perhaps originally "fit, adequate, belonging together," from PIE root *ghedh- "to unite, be associated, suitable" (source also of Sanskrit gadh- "seize (booty)," Old Church Slavonic godu "favorable time," Russian godnyi "fit, suitable," Lithuanian goda "honor," Old English gædrian "to gather, to take up together").
Sense of "kind, benevolent" is from late Old English in reference to persons or God, from mid-14c. of actions. Middle English sense of "holy" is preserved in Good Friday. That of "friendly, gracious" is from c. 1200. Meaning "fortunate, prosperous, favorable" was in late Old English. As an expression of satisfaction, from early 15c. Of persons, "skilled (at a profession or occupation), expert," in late Old English, now typically with at; in Middle English with of or to. Of children, "well-behaved," by 1690s. Of money, "not debased, standard as to value," from late 14c. From c. 1200 of numbers or quantities, "large, great," of time or distance, "long;" good while "a considerable time" is from c. 1300; good way "a great distance" is mid-15c.
Why then, can one desire too much of a good thing. ["As You Like It"]
As good as "practically, virtually" is from mid-14c.; to be good for "beneficial to" is from late 14c. To make good "repay (costs, expenses), atone for (a sin or an offense)" is from late 14c. To have a good mind "have an earnest desire" (to do something) is from c. 1500. Good deed, good works were in Old English as "an act of piety;" good deed specifically as "act of service to others" was reinforced early 20c. by Boy Scouting. Good turn is from c. 1400. Good sport, of persons, is from 1906. The good book "the Bible" attested from 1801, originally in missionary literature describing the language of conversion efforts in American Indian tribes. Good to go is attested from 1989.
sixth day of the week, Old English frigedæg "Friday, Frigga's day," from Frige, genitive of *Frigu (see Frigg), Germanic goddess of married love. The day name is a West Germanic translation of Latin dies Veneris "day of (the planet) Venus," which itself translated Greek Aphrodites hēmera.
Compare Old Norse frijadagr, Old Frisian frigendei, Middle Dutch vridach, Dutch vrijdag, German Freitag "Friday," and the Latin-derived cognates Old French vendresdi, French vendredi, Spanish viernes. In Germanic religion, Freya (q.v.) corresponds more closely in character to Venus than Frigg does, and some early Icelandic writers used Freyjudagr for "Friday."
A fast-day in the Church, hence Friday face (17c.) for a gloomy countenance. Black Friday as the name for the busy shopping day after U.S. Thanksgiving holiday is said to date from 1960s and perhaps was coined by those who had the job of controlling the crowds, not by the merchants; earlier it was used principally of Fridays when financial markets crashed (1866, 1869, 1873).
Old English god (with a long "o"), "that which is good, a good thing; goodness; advantage, benefit; gift; virtue; property;" from good (adj.). Meaning "the good side" (of something) is from 1660s. Phrase for good "finally, permanently" attested from 1711, a shortening of for good and all (16c.). Middle English had for good ne ylle (early 15c.) "for good nor ill," thus "under any circumstance."
1928, from the noun phrase, from good (adj.) + time (n.). Expression to have a good time "enjoy oneself" attested from 1822; earlier have a good time of it (1771). To make good time "go fast" is from 1838. In Middle English, good time was "prosperous time," also "high time" (that something be done).
salutation in parting, also goodbye, good bye, good-by, 1590s, from godbwye (1570s), a contraction of God be with ye (late 14c.), influenced by good-day, good evening, etc. As a noun from 1570s. Intermediate forms in 16c. include God be wy you, God b'uy, God buoye, God buy, etc.
"useless, valueless," 1908, from phrase no good "good for nothing." As a noun, recorded by 1924; the variant no-goodnik (see -nik) is attested by 1959.