The noun loot was first attested in a 1788 English-Hindi dictionary, with the same definition as today. It wasn't used in the context of actual English until the mid-nineteenth century, but was quickly picked up after that. As Hindi lut, it pretty much meant the same thing, and that comes from the Sanskrit verb lunt, meaning "to rob", so still very similar. Finally, it's thought that lunt derives from the Proto-Indo-European reconstruction  reup, meaning "snatch". If you search literary usage of loot over time, you'll see that loot was in use well before 1788; that's because, in certain English dialects, loot has also referred to a type of ladle (this sense has a completely different etymology, coming from Dutch loet​) and served as a slang word for lieutenant. The verb form first appeared in 1842.

Today, the word spiel means "persuasive speech", but it comes from a German word meaning "performance" or "game", possibly by way of Yiddish shpil, which meant "game" or "fun". That traces to the Old High German and Proto-West Germanic words spil, with the same definition. Finally, spil has an uncertain etymology, and tenuous connections have been made to a Latvian word for "pinch". Spiel can also serve as a verb meaning "to gamble" or "play music", with both of those meanings also tracing to the German noun, and, in Scottish English, it can mean "curling match" - that's an unrelated shortening of the (ultimately Dutch) word bonspiel, which referred to matches in games or sports in general. Literary usage of spiel has been steadily increasing over time, with a peak in 2014.

In Revelation 13:18, the Bible (depending on the version) says "let him who has understanding calculate the number of the beast, for the number is that of a man; and his number is six hundred and sixty-six." In modern culture, this became associated with the devil because of confusion with his beast. But what was the original meaning behind the number? The leading theory is that it was a hidden insult against Roman emperor Nero. In Hebrew, letters are also used to represent numbers, and the numbers that added up to 666 in the translation could also spell out NRON QSR (there are no vowels) or "Neron Kesar", the Hebrew way to write Nero Caesar. The timeline would check out, too: the Book of Revelation is thought to have been written about 30 years after Nero's death, a time when there was a widespread belief that Nero would return to life.

The phrase we stan is an increasingly prominent slang word among Gen Z and Millenial people used to indicate strong agreement or approval of something (e.g. we stan this band). It's thought to trace to a 2000 hip hong song by Eminem called Stan, which was about an extremely obsessive fan called Stan. The next recorded usage is from a 2001 diss track by rapper Nas, where he used it as a synonym of words like "phony" and "fake". For a while, the proper noun was negative and associated with overzealous people, but eventually it came to be viewed in a better light. It was first recorded on Urban Dictionary in 2006, first used as a verb in a 2008 verb, and, according to Google Trends, has been steadily increasing in usage since. The plural form emerged to imply that many people support the viewpoint.

I've never given any thought to the phrase parting shot - I guess I just assumed that it was a shot made right before you depart - so I was shocked to learn that it's actually a folk etymologization of the phrase Parthian shot! That term referred to a particularly difficult military tactic used by the Parthinian people of Ancient Persia wherein retreating archers on horseback would turn around on the horse and shoot behind them. This came to be a metaphor in English around the nineteenth century, and was corrupted into the modern form relatively quickly. Parthinian is the endonym for Parthia, which comes from the Old Persian root p-r-th-n, which also referred to the general region. According to Google NGrams, literary usage of parting shot peaked in 2015 and has been declining since.