Discussions on the Internet use tons of ASOIAF argot. Some of them are obvious, like Areo Hotah “The Camera that Rides”; some of them are inside jokes. Here’s a list.
1. Cleganebowl (GET HYPE)
Cleganebowl is amongst the most anticipated events in Game of Thrones/ASOIAF, and according to its official subreddit, ‘Sandor and Gregor Clegane will fight each other, as foretold, and the winner will be the fans.’ The theory revolves around Maggy the Frog’s prophecy of the ‘valonqar’, which is High Valyrian for ‘little brother’. Sandor (or the Hound) is Gregor’s (or the Mountain’s) younger brother. The prophesied fight is Cersei Lannister’s trial by combat, with the Mountain as Cersei’s champion, and the Hound fighting on behalf of the Faith. The video above explains it all, with the necessary air horn sound effects and hip-hop that anything associated with Cleganebowl solicits. Season 6 of the show got rid of the trial by combat, but the Cleganebowl legion continues to thrive.
2. Stannis the Mannis
Stannis “the Mannis”, or “Stan the Man” for short, is Stannis Baratheon’s fan nickname. Every rightful king has his (or her) fan following, and Stannis’ is particularly fervent. It rhymes, for one thing, and ‘Mannis’ (supposedly) emphasises on his masculinity, especially his military strategizing. It’s essentially a nickname. You can get an impressive poster here.
3. “Oh, my sweet summer child”
“Oh, my sweet summer child,” is a line from Old Nan’s monologue from A Game of Thrones, Bran IV, when Old Nan tells Bran of the Long Night and the White Walkers. In Westeros, seasons last decades; some winters are so long that people live and die without ever seeing a summer. A ‘summer child’ is a person who was born during the summer and has never experienced a winter; it’s also a metaphor for somebody who’s naive and unaware of life’s harsh realities. Redditors at r/gameofthrones are fond of it.
“DaKingInDaNorf”, usually written in capitals and followed with several exclamation marks, is an affectionate parody of “The King in the North!” said with a Northern accent. When Robb Stark was first crowned in Season 1, the Northern lords rose and took up the cry. This scene was echoed in Season 6, when the remaining Northern lords swore allegiance to Jon Snow. Any mention of Jon or the North in general on Reddit receives several of these in response.
5. The Purple Wedding
The Purple Wedding is possibly the most widely used fan-term in Game of Thrones. It refers to Joffrey’s death and assassination, and the ‘purple’ is an allusion to the purple amethysts in Sansa’s hairnet, which were instrumental in poisoning Joffrey’s purple wine, the drinking of which resulted in Joffrey’s face turning purple (because he was choking). Joffrey’s wedding didn’t have an official book or show name, but fans picked up on the officially named Red Wedding, and adjusted it for Joffrey. It’s so popular that even GRRM uses it.
6. Twenty Good Men
Twenty Good Men is a Ramsay Bolton joke; a GRRM joke as a whole, actually. GRRM is fond of using the phrase “good men” to refer to soldiers and armies and their like, and in S05E08, Ramsay says “I don’t need an army. I need twenty good men.” The comments on this Reddit post explain it all.
7. The Ides of Marsh
At the end of A Dance with Dragons, Lord Commander Jon Snow is stabbed to death by rebelling members of the Night’s Watch, much like Julius Caesar’s assassination. The Game of Thrones variation changes ‘March’ to ‘Marsh’, which is a reference to Bowen Marsh, Lord Steward of the Night’s Watch, and one of the conspirators who helped kill Snow. It’s a spoiler-free way of mentioning Jon’s assassination.
This page on TV Tropes has a lot more.