mickle (adj., n.)

c. 1200, "great in quantity or extent" (also "great in size, big, large," a sense now obsolete), a worn-down form (by loss of unaccented last syllable) of Middle English muchel "large, tall; many, in a large amount; great, formidable," from Old English micel "great in amount or extent," from Proto-Germanic *mekilaz, from PIE root *meg- "great."

As a noun, "a large quantity, a great deal," and as an adverb, "in a great degree, intensely, extensively," from c. 1200. Since 17c. the adverb has been much-used as a prefix to participial forms to make compound adjectives. For vowel evolution, see bury.

Too much was used from late 14c. in the senses "astonishing, incredible," also "too offensive, unforgivable;" by 1530s as "more than can be endured." The meaning "excellent" is attested by 1937 in jazz slang. Hence too-muchness (1875).

Much-what "various things, this and that" (late 14c.) was "Very common in the 17th c." [OED, 1989] and turns up in an 1899 book of Virginia folk-speech as well as "Ulysses."

Old English great "big, tall, thick, stout, massive; coarse," from West Germanic *grauta- "coarse, thick" (source also of Old Saxon grot, Old Frisian grat, Dutch groot, German groß "great"). If the original sense was "coarse," it is perhaps from PIE root *ghreu- "to rub, grind," via the notion of "coarse grain," then "coarse," then "great;" but "the connextion is not free from difficulty" [OED].

It took over much of the sense of Middle English mickle, and itself now is largely superseded by big and large except in reference to non-material things. In the sense of "excellent, wonderful" great is attested from 1848.

Great White Way "Broadway in New York City" is from 1901, in reference to brilliant street illumination. The Great Lakes of North America so called by 1726, perhaps 1690s. Great Spirit "high deity of the North American Indians," 1703, originally translates Ojibwa kitchi manitou. The Great War originally (1887) referred to the Napoleonic Wars, later (1914) to what we now call World War I (see world).

"The Great War" — as, until the fall of France, the British continued to call the First World War in order to avoid admitting to themselves that they were now again engaged in a war of the same magnitude. [Arnold Toynbee, "Experiences," 1969]

Also formerly with a verb form, Old English greatian "to become enlarged," Middle English greaten "to become larger, increase, grow; become visibly pregnant," which became archaic after 17c.