Online Etymology Dictionary

mirth (n.): Old English myrgð "joy, pleasure," from Proto-Germanic *murgitha (source also of Middle Dutch merchte), noun of quality from *murgjo- (see merry; also see -th (2)). Mirthquake "entertainment that excites convulsive laughter" first attested 1928, in reference to Harold Lloyd movies.
mirthful (adj.): c. 1300, from mirth + -ful. Related: Mirthfully; mirthfulness.
mirthless (adj.): late 14c., from mirth + -less. Related: Mirthlessly.
merriment (n.): 1570s, "comedic entertainment," from merry + -ment. General sense of "mirth" is from 1580s.
gaily (adj.): also gayly, "with mirth and frolic," late 14c., from Middle English gai (see gay) + -ly (2). "The spelling gaily is the more common, and is supported by the only existing analogy, that of daily" [OED].
jollification (n.): "mirth, scene or occasion of merrymaking," 1769, from jolly + -fication. Shortened form jolly (1905) led to phrase get (one's) jollies "have fun" (1957). Spenser has jolliment (1590).
jouissance (n.): late 15c., "possession and use" (of something), from Old French joissance, from joissant "happy, glad," present participle of joir "to enjoy, take delight in, take pleasure in" (see enjoy). Meaning "enjoyment, joy, mirth" is from 1570s.
gaiety (n.): "cheerfulness, mirth," 1630s, from French gaieté (Old French gaiete, 12c.), from gai "gay" (see gay). In the 1890s, in Britain, especially with reference to a London theater of that name, and the kind of musical shows and dancing girls it presented.
hoyden (n.): "ill-bred, boisterous young female," 1670s; earlier "rude, boorish fellow" (1590s), of uncertain origin; perhaps from Dutch heiden "rustic, uncivilized man," from Middle Dutch heiden "heathen," from Proto-Germanic *haithinaz- (see heathen). OED points to Elizabethan hoit "indulge in riotous and noisy mirth" in Nares.
Euphrosyne: name of one of the three Graces in Greek mythology, via Latin, from Greek Euphrosyne, literally "mirth, merriment," from euphron "cheerful, merry, of a good mind," from eu "well, good" (see eu-) + phren (genitive phrenos) "mind," which is of unknown origin.
frolic (v.): "make merry, have fun, romp playfully," 1580s, from frolic (adj.) "joyous, merry, full of mirth" (1530s), from Middle Dutch vrolyc "happy," a compound of vro- "merry, glad" + lyc "like" (see like (adj.)). The first part of the compound is cognate with Old Norse frar "swift," Middle English frow "hasty," from PIE *preu- "to hop" (see frog (n.1)), giving the whole an etymological sense akin to "jumping for joy." Similar formation in German fröhlich "happy." Related: Frolicked; frolicking. As a noun from 1610s.
glee (n.): Old English gliu, gliw, gleow "entertainment, mirth (usually implying music); jest, play, sport," also "music" and "mockery," presumably from a Proto-Germanic *gleujam but absent in other Germanic languages except for the rare Old Norse gly "joy;" probably related to the group of Germanic words in gl- with senses of "shining; smooth; radiant; joyful" (see glad). A poetry word in Old English and Middle English, obsolete c. 1500-c. 1700, it somehow found its way back to currency late 18c. In Old English, an entertainer was a gleoman (female gleo-mægden).

Glee club (1814) is from the secondary sense of "musical composition for three or more solo voices, unaccompanied, in contrasting movement" (1650s), a form of musical entertainment that flourished 1760-1830.
dream (n.): mid-13c. in the sense "sequence of sensations passing through a sleeping person's mind" (also as a verb), probably related to Old Norse draumr, Danish drøm, Swedish dröm, Old Saxon drom "merriment, noise," Old Frisian dram "dream," Dutch droom, Old High German troum, German traum "dream," perhaps from Proto-Germanic *draugmas "deception, illusion, phantasm" (source also of Old Saxon bidriogan, Old High German triogan, German trügen "to deceive, delude," Old Norse draugr "ghost, apparition"). Possible cognates outside Germanic are Sanskrit druh- "seek to harm, injure," Avestan druz- "lie, deceive."

But Old English dream meant only "joy, mirth, noisy merriment," also "music." And much study has failed to prove that Old English dream is the root of the modern word for "sleeping vision," despite being identical in spelling. Either the meaning of the word changed dramatically or "vision" was an unrecorded secondary Old English meaning of dream, or there are two separate words here. OED offers this theory: "It seems as if the presence of dream 'joy, mirth, music,' had caused dream 'dream' to be avoided, at least in literature, and swefn, lit. 'sleep,' to be substituted ...."

Words for "sleeping vision" in Old English were mæting and swefn. Old English swefn originally meant "sleep," as did a great many Indo-European "dream" nouns, such as Lithuanian sapnas, Old Church Slavonic sunu, and the Romanic words (French songe, Spanish sueño, Italian sogno all from Latin somnium (from PIE *swep-no-; cognate with Greek hypnos; see somnolence; Old English swefn is from the same root). Dream in the sense of "ideal or aspiration" is from 1931, from earlier sense of "something of dream-like beauty or charm" (1888).
charade (n.): 1776, from French charade (18c.), probably from Provençal charrado "long talk, chatter," of obscure origin, perhaps from charrar "to chatter, gossip," of echoic origin. Compare Italian ciarlare, Spanish charlar "to talk, prattle." Originally not silent, but relying rather on enigmatic descriptions of the words or syllables.
As we have ever made it a Rule to shew our Attention to the Reader, by 'catching the Manners living, as they rise,' as Mr. Pope expresses it, we think ourselves obliged to give Place to the following Specimens of a new Kind of SMALL WIT, which, for some Weeks past, has been the Subject of Conversation in almost every Society, from the Court to the Cottage. The CHARADE is, in fact, a near Relation of the old Rebus. It is usually formed from a Word of two Syllables; the first Syllable is described by the Writer; then the second; they are afterwards united and the whole Word marked out .... [supplement to "The Universal Magazine of Knowledge and Pleasure," volumes 58-59, 1776]
Among the examples given are:

My first makes all nature appear of one face;
At the next we find music, and beauty and grace;
And, if this Charade is most easily read,
I think that the third shou'd be thrown at my head.

[The answer is "snow-ball."]

The silent form, the main modern form, was at first a variant known as dumb charades and at first it was not a speed contest; rather it adhered to the old pattern, and the performing team acted out all the parts in order before the audience team began to guess.
There is one species of charade which is performed solely by "dumb motions," somewhat resembling the child's game of "trades and professions"; but the acting charade is a much more amusing, and more difficult matter. ["Goldoni, and Modern Italian Comedy," in "The Foreign And Colonial Quarterly Review," Volume 6, 1846]
An 1850 book, "Acting Charades," reports that Charades en Action were all the rage in French society, and that "Lately, the game has been introduced into the drawing-rooms of a few mirth-loving Englishmen. Its success has been tremendous." Welsh siarad obviously is a loan-word from French or English, but its meaning of "speak, a talk" is closer to the Provençal original.