The episode title is a play on Ernest Hemingway's 1929 novel A Farewell to Arms, a romance between an American ambulance driver in the Italian Army and an English nurse, set against the backdrop of World War I.
Qo'noS is the Klingon Homeworld, last seen in DIS: "Point of Light" or, chronologically in-universe in DS9: "The House of Quark".
Ma'ah first appeared in LD: "wej Duj", and was last seen in LD: "The Inner Fight". The targ may be the pet he inherited from his previous captain, Dorg, whom he killed and then attained his own rank and the IKS Che’Ta’. The farming outfit Ma'ah wears echoes the one the older Picard wore in TNG: "All Good Things..." and he is sipping from a Klingon bloodwine mug. We also see how bloodwine is made - apparently harvested from worms grown in the soil.
The usual title sequence is replaced by cinematic-style titles complete with rousing music. Mariner and Ma'ah befriended (sort of) each other in "The Inner Fight" on Sherbal V, which is why she's calling.
A petaQ is a Klingon epithet, which can be loosely translated as "weirdo" (from taQ, to be weird, and pe, an imperative you). The Klingon axe-throwers are using various blades, but the one flying across the screen is a mek'leth, a two-pronged dagger generally used for throat slashing and disemboweling (ENT: "Marauders"). bahgol is a warm tea-like beverage (DS9: "Blood Oath").
One of the members of the Klingon band is playing a concertina like DS9’s Klingon Chef in DS9: “Playing God”. Ma'ah tells K'Elarra he did not expect to see her in this pugh gegh (as per the closed captioning) but I suspect this to be an error and it should be pugh qegh, which translates to "barrel/vat of dregs", which makes the bartender's insulted reaction more logical. par'Mach means "love" (but with more aggressive overtones). K’Elarra’s manhandling of Ma’ah and her sniffing him are typical of Klingon mating practices (TNG: “The Emissary”) and her “boob window” commented on by Mariner appeared first on Klingon females with the Duras sisters in TNG: “Redemption”. K’Elarra is voiced by Mary Chieffo, who played L’Rell in DIS.
Boimler's beard has progressed to an actual moustache now although his goatee is still a work in progress, charitably speaking. cha'DIch can be loosely translated as "second", in the sense of someone who speaks or acts on behalf of the principal in a duel, or in other contexts a confidant or mentee.
Cerritos is in orbit around Praxon IV. Tendi refers to when Migleemo fought the Orion warrior B'eth in LD: "Old Friends, New Planets". We are told Migleemo's species (Klowahkans) for the first time, and are told they invented warp travel to discover "strange new meals" as opposed to strange new worlds. This also explains Migleemo's penchant for food metaphors. Whether the planet name is a pun on "cloaca" l leave for speculation.
'urwI'pu' means "traitors". Martok’s legendary killing of them took place in the Ketha Lowlands, a poor area of Qo’noS, where he said his family was from (DS9: “Once More Unto the Breach”). A d'k tagh (misspelt diktagh) is a traditional Klingon warrior's dagger first seen in ST III. Boimler's fear of skiing cropped up last episode in LD: "The Best Exotic Nanite Hotel". He mentions the Ritual of J'ethurgh and the Ritual of Forced Conscription, both first mentions.
bIj means punishment, which is usually used as a verb, not a noun. But the term “Experience bIj!” is a particularly deep cut from the Star Trek: The Next Generation - Interactive VCR Board Game - A Klingon Challenge, where during the game Captain Kavok (played by Robert O’Reilly who was Gowron on TNG and DS9) occasionally says this to one of the players who must then draw a Bij card and do what it says.
K'orin is a Klingon General and friend of Mariner's, who was last seen in LD: "Envoys". quv beq means "crew of honor". lujwI'pu' means "losers". Councilor Enaj is “Jane” spelled backwards.
Mordanian may refer to the inhabitants of Mordan IV (TNG: "Too Short a Season").
Kahless refers to Kahless the Unforgetable, a semi-mythical figure who was the greatest warrior in Klingon history as well as the first Emperor (TOS: “The Savage Curtain”).
Fekh’lr is the guardian of Grethor, the Klingon underworld (TNG: “Devil’s Due”). While we’ve known that part of Kahless’ legend is that he conquered a group called the Fekh’lri, we’ve never actually connected them to the mythical Fekh’lr on screen. In Star Trek Online, however, they do resemble Fekh’lr and were foot soldiers of Kahless’s enemy Molor (created by the Dominion), and were banished to Gre’thor with him. Boimler’s remark suggests that the Fekh’lri were minions of Fekh’lr as this story has Kahless killing Fekh’lr.
Painstiks (or pain sticks) were first seen being used in the Klingon Rite of Ascension, marking the occasion of a Klingon child reaching the Age of Inclusion and becoming a Klingon warrior (TNG: “The Icarus Factor”). darseks are the main currency used in the Klingon Empire (TNG: “Firstborn”). tagh-jaj qaD can be translated as “begin the challenge day”.
Boimler notes that the maximum painstik voltage is 30,000 volts. Whether or not an electrical shock is lethal really depends on both voltage and amperage, where voltage is the force of electrical power passing through but current (amps) is the rate of flow.
A hogfish (on Earth at least) is a type of wrasse living in the Western Atlantic, so called because of its elongated snout. It doesn’t have more than two eyes, though. Enara Prime is a planet in the Delta Quadrant, home to the Enarans, a telepathic species (VOY: “Remember”).
HIq’aD comes from HIq (ale, wine) and ’aD (blood vessel), so I’d imagine it’s an epithet saying that Malor’s a drunk.
Boimler references his brief transfer to the Titan at the end of Season 2 and the first few episodes of season 3.
qoH means “fool”. Klingons can’t transfer ships except with a two-thirds vote of the Oversight Council.
chatlh means “thick soup”, but it’s also slang for “nonsense”. Sto-vo-kor is the Klingon equivalent of Valhalla. Ma’ah uses a bat’leth while Bragh fights with a gin’tak battle spear. The armor Bragh crashes into before he grabs the spear is a Klingon Honor Guard set from STO. The Klingon blood spilled is pink, as per ST VI, although this has been inconsistent through Star Trek, which generally shows Klingon blood as red.
Mariner discovers that the dimensional rifts are not natural, but someone is causing them. toDuj means “courage”.
Malor claims he sees Kahless, the “original one”. A clone of Kahless was created by the monks of Boreth in TNG: “Rightful Heir”, who eventually became the ceremonial Emperor/Head of State of the Empire. He also says the original was “good at imitating voices”, which indeed the Excalbian recreation was when he imitated Surak’s voice in TOS: “The Savage Curtain”.
I might also add that Ma'ah's family career is very similar to Boimler's in some aspects, staying in line with how in Wej Duj he was supposed to be a Klingon analog of Boimler.