"too great in amount, excessive, immoderate," c. 1300, from over- + much (q.v.). As an adverb, "excessively, immoderately," from late 14c. As a noun, "an excessive amount," c. 1300. Old English had cognate ofermicel. Middle English had also overmore "further, in addition, moreover" (late 14c.).
Entries linking to overmuch
word-forming element meaning variously "above; highest; across; higher in power or authority; too much; above normal; outer; beyond in time, too long," from Old English ofer (from PIE root *uper "over"). Over and its Germanic relations were widely used as prefixes, and sometimes could be used with negative force. This is rare in Modern English, but compare Gothic ufarmunnon "to forget," ufar-swaran "to swear falsely;" Old English ofercræft "fraud."
In some of its uses, moreover, over is a movable element, which can be prefixed at will to almost any verb or adjective of suitable sense, as freely as an adjective can be placed before a substantive or an adverb before an adjective. [OED]
Among the old words not now existing are Old English oferlufu (Middle English oferlufe), literally "over-love," hence "excessive or immoderate love." Over- in Middle English also could carry a sense of "too little, below normal," as in over-lyght "of too little weight" (c. 1400), overlitel "too small" (mid-14c.), overshort, etc.
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." Much-what "various things, this and that" (late 14c.) was "Very common in the 17th c." [OED] and turns up in an 1899 book of Virginia folk-speech as well as "Ulysses."
let's not blame them overmuch
showed overmuch affection