amusing (adj.)youdaoicibaDictYouDict[amusing 词源字典]
c. 1600, "cheating;" present participle adjective from amuse (v.). Sense of "interesting" is from 1712; that of "pleasantly entertaining, tickling to the fancy" is from 1826. Noted late 1920s as a vogue word. Amusive has been tried in all senses since 18c. and might be useful, but it never caught on. Related: Amusingly.[amusing etymology, amusing origin, 英语词源]
comedy (n.)youdaoicibaDictYouDict
late 14c., from Old French comedie (14c., "a poem," not in the theatrical sense), from Latin comoedia, from Greek komoidia "a comedy, amusing spectacle," probably from komodios "actor or singer in the revels," from komos "revel, carousal, merry-making, festival," + aoidos "singer, poet," from aeidein "to sing," related to oide (see ode).
The passage on the nature of comedy in the Poetic of Aristotle is unfortunately lost, but if we can trust stray hints on the subject, his definition of comedy (which applied mainly to Menander) ran parallel to that of tragedy, and described the art as a purification of certain affections of our nature, not by terror and pity, but by laughter and ridicule. [Rev. J.P. Mahaffy, "A History of Classical Greek Literature," London, 1895]
The classical sense of the word, then, was "amusing play or performance," which is similar to the modern one, but in the Middle Ages the word came to mean poems and stories generally (albeit ones with happy endings), and the earliest English sense is "narrative poem" (such as Dante's "Commedia"). Generalized sense of "quality of being amusing" dates from 1877.
Comedy aims at entertaining by the fidelity with which it presents life as we know it, farce at raising laughter by the outrageous absurdity of the situation or characters exhibited, & burlesque at tickling the fancy of the audience by caricaturing plays or actors with whose style it is familiar. [Fowler]
entertain (v.)youdaoicibaDictYouDict
late 15c., "to keep up, maintain, to keep (someone) in a certain frame of mind," from Middle French entretenir, from Old French entretenir "hold together, stick together, support" (12c.), from entre- "among" (from Latin inter; see inter-) + tenir "to hold" (from Latin tenere; see tenet).

Sense of "have a guest" is late 15c.; that of "gratify, amuse" is 1620s. Meaning "to allow (something) to consideration, take into the mind" (of opinions, notions, etc.) is 1610s. Related: Entertained; entertaining.
gallant (adj.)youdaoicibaDictYouDict
mid-15c., "showy, finely dressed; gay, merry," from Old French galant "courteous," earlier "amusing, entertaining; lively, bold" (14c.), present participle of galer "rejoice, make merry," which is of uncertain origin. Perhaps from a Latinized verb formed from Frankish *wala- "good, well," from Proto-Germanic *wal- (source also of Old High German wallon "to wander, go on a pilgrimage"), from PIE root *wel- (2) "to wish, will" (see will (v.)), "but the transition of sense offers difficulties that are not fully cleared up" [OED]. Sense of "politely attentive to women" was adopted early 17c. from French. Attempts to distinguish this sense by accent are an 18c. artifice.
rich (adj.)youdaoicibaDictYouDict
Old English rice "strong, powerful; great, mighty; of high rank," in later Old English "wealthy," from Proto-Germanic *rikijaz (cognates: Old Norse rikr, Swedish rik, Danish rig, Old Frisian rike "wealthy, mighty," Dutch rijk, Old High German rihhi "ruler, powerful, rich," German reich "rich," Gothic reiks "ruler, powerful, rich"), borrowed from a Celtic source akin to Gaulish *rix, Old Irish ri (genitive rig) "king," from PIE root *reg- "move in a straight line," hence, "direct, rule" (see rex).

The form of the word was influenced in Middle English by Old French riche "wealthy, magnificent, sumptuous," which is, with Spanish rico, Italian ricco, from Frankish *riki "powerful," or some other cognate Germanic source.

Old English also had a noun, rice "rule, reign, power, might; authority; empire." The evolution of the word reflects a connection between wealth and power in the ancient world. Of food and colors, from early 14c.; of sounds, from 1590s. Sense of "entertaining, amusing" is recorded from 1760. The noun meaning "the wealthy" was in Old English.
rotary (adj.)youdaoicibaDictYouDict
1731, from Medieval Latin rotarius "pertaining to wheels," from Latin rota "a wheel, a potter's wheel; wheel for torture," from PIE root *ret- "to run, to turn, to roll" (cognates: Sanskrit rathah "car, chariot;" Avestan ratho; Lithuanian ratas "wheel," ritu "I roll;" Old High German rad, German Rad, Dutch rad, Old Frisian reth, Old Saxon rath, Old Irish roth, Welsh rhod "carriage wheel"). The international service club (founded by Paul P. Harris in Chicago in 1905) so called from the practice of clubs entertaining in rotation. Hence Rotarian (1911).
divertimentoyoudaoicibaDictYouDict
"A light and entertaining composition, typically one in the form of a suite for chamber orchestra", Mid 18th century (denoting a diversion or amusement): Italian, literally 'diversion'.