1540s, "time of merrymaking before Lent," from French carnaval, from Italian carnevale "Shrove Tuesday," from older Italian forms such as Milanese *carnelevale, Old Pisan carnelevare "to remove meat," literally "raising flesh," from Latin caro "flesh" (originally "a piece of flesh," from PIE root *sker- (1) "to cut") + levare "lighten, raise, remove" (from PIE root *legwh- "not heavy, having little weight").
Folk etymology has it from Medieval Latin carne vale " 'flesh, farewell!' " Attested from 1590s in the figurative sense of "feasting or revelry in general." The meaning "a circus or amusement fair" is attested by 1926 in American English.
1550s, "mildness or gentleness shown in exercise of authority," from Latin clementia "calmness, gentleness," from clemens "calm, mild," related to clinare "to lean," often said to be from PIE root *klei- "to lean" + participial suffix -menos (also in alumnus). For sense evolution, compare inclined in secondary meaning "disposed favorably." But de Vaan is dubious on phonological grounds.
Clemency is exercised only toward offenders, being especially the attribute of those in exalted places having power to remit or lighten penalty. [Century Dictionary]
Earlier in same sense was clemence (late 15c.). Meaning "mildness of weather or climate" is 1660s (a sense also in Latin); clement (adj.) is older in both senses (late 15c. and 1620s respectively) but now is used only in negation and only of the weather.
"the female of the domestic fowl," Old English henn "hen," from West Germanic *hannjo (source also of Old Frisian henn, Middle Dutch henne, Old High German henna), fem. of *hanan- "male fowl, cock" (source of Old English hana "cock"), literally "bird who sings (for sunrise)," from PIE root *kan- "to sing."
The original masculine word survives in German (Hahn "cock"), Swedish, Danish, etc. German also has a generic form, Huhn, for either gender of the bird. Extension to "female of any bird species" is early 14c. in English.
Hen as slang for "woman" dates from 1620s; hence hen party "gathering of women," first recorded 1887. To be mad as a wet hen is from 1823, but the figure was used to indicate other states: As wanton as a wet hen is in "Scots Proverbs" (1813). Among Middle English proverbial expressions was nice as a nonne hen "over-refined, fastidiously wanton" (c. 1500); to singen so hen in snowe "sing miserably," literally "sing like a hen in snow" (c. 1200). The figure of the hen with one chick dates to 1590s. Hen's teeth as a figure of scarceness is attested by 1838.
Some, on the contrary, are viciously opposite to these, who act so tamely and so coldly, that when they ought to be angry, to thunder and lighten, as one may say, they are no fuller of Heat, than a wet Hen, as the Saying is; .... ["Life of Mr. Thomas Betterton," London, 1710]
Orth. Out upon you for a dastardly Fellow; you han't the Courage of a wet Hen. ["A Sermon Preached at St. Mary-le-Bow, March 27, 1704"]