mid-15c., "pretend poverty," probably from Old French muchier, mucier "to hide, sulk, conceal, hide away, keep out of sight," a word of uncertain origin, perhaps from Celtic or Germanic (Liberman prefers the latter, Klein the former). Also compare Middle English michen "to pilfer (small things)," mid-15c., perhaps from an Old English *mycan (compare Old High German muhhan "rob, ambush, waylay"). Or the word may be a variant of Middle English mucchen "to hoard, be stingy" (c. 1300), probably originally "to keep coins in one's nightcap," from mucche "nightcap," from Middle Dutch muste "cap, nightcap," ultimately from Medieval Latin almucia, also a word of unknown origin. Sense of "sponge off others" is recorded by 1857.
Whatever the distant origin of mooch, the [Germanic] verb *mycan and its cognates have been part of European slang for at least two millennia. [Liberman]
It appears to be a remarkably long-lived bit of slang. Related: Mooched; mooching. As a noun meaning "a moocher," from 1914; as "action of mooching," by 1867.
"emotional condition, state of mind as regards passion or feeling," c. 1300, from Old English mod "heart, frame of mind, spirit; courage, arrogance, pride; power, violence" (also used to translate Latin animus, mens), from Proto-Germanic *mōda- (source also of Old Saxon mod "mind, courage," Old Frisian mod "intellect, mind, intention," Old Norse moðr "wrath, anger," Middle Dutch moet, Dutch moed, Old High German muot, German Mut "courage," Gothic moþs "courage, anger"), a word of unknown origin (Boutkan finds no acceptable IE etymology).
A much more vigorous word in Anglo-Saxon than currently, and used widely in compounds (such as modcræftig "intelligent," modful "proud"). The Old English senses now are obsolete. Meaning "a fit of bad temper; sullenness, sudden anger" is by 1859. To be in the mood "in a state of mind to be willing (to do or omit something)" is from 1580s. First record of mood swings is by 1939.
"grammatical form indicating the function of a verb," 1570s, an alteration of mode (n.1). The grammatical and musical (1590s) usages of it influenced the meaning of mood (n.1) in such phrases as light-hearted mood, but it is worth remembering that the two moods have no etymological relationship. Also used in traditional logic (1560s) as a variant of mode.
"hold a second job, especially at night," 1957 (implied in the verbal noun moonlighting), from moonlighter "one who takes a second job after hours" (1954), from the notion of working by the light of the moon; see moonlight (n.). Earlier the verb had been used to mean "commit crimes at night" (1882), from moonlighter in reference to members of organized bands that carried on agrarian outrages in Ireland. And compare moonshine. Moonlighter in American English meant "one of a party who go about serenading on moonlit nights" (by 1897).
"a long time," 1821, often in phrases indicating something rarely occurring. Compare at the Greek calends (from an ancient Roman phrase alluding to the fact that the Greeks had nothing corresponding to the Roman calends), and the native in the reign of Queen Dick and Saint Geoffrey's Day "Never, there being no saint of that name," reported in Grose (1788). Nevermass "date which never comes" is from 1540s. Blue moon is suggested earliest in this couplet from 1528:
Yf they say the mone is blewe,
We must beleve that it is true.
Though this might refer to calendrical calculations by the Church. Thus the general "rareness" sense of the term is difficult to disentangle from the specific calendrical one (commonly misinterpreted as "second full moon in a calendar month," but actually a quarterly calculation). In either case, the sense of blue here is obscure. Literal blue moons do sometimes occur under extreme atmospheric conditions.