peak

Peak is a word you have to place before you can read. Two slang senses run at once, and they point in opposite directions.

The online sense is praise, and it is the more common one worldwide today. It grew out of anime fandom, where "peak fiction" crowns the best story ever, and it spread until "this is peak" became a general superlative for food, music, games, anything. The logic is the mountain: the top, the highest point.

The British sense is the reverse. In London speech, and across UK youth slang, "that's peak" means that is bad, harsh, unfair, or unlucky. Someone loses their phone and their friends say "rah, that's peak" in sympathy. This sense is older than the internet one, and in Britain it is still the default reading. That makes the word a genuine trap. The same three words are praise in one country and condolence in another.

Context does the sorting. "Peak fiction" is always praise. "That's peak" from a British speaker is almost always sympathy.

Two separate slang lives grew from the same standard word, and the exact coinage of each is unclear.

The British negative sense is documented first. Green's Dictionary of Slang's earliest citation is a 2012 Guardian piece glossing peak as "a bit terrible." Its trail then runs through grime, with lyrics by Wiley in 2014 and Skepta in 2016, into the drill-era glossaries. Wiktionary files the sense under Multicultural London English. So the credit belongs to London's multicultural youth speech and the grime scene that carried it. How "highest point" flipped into "worst outcome" is not settled, and no source documents the route properly.

The positive sense is internet fandom's. Meme trackers date "peak fiction" to anime message boards around 2018, and it spread through the early 2020s until peak on its own became praise. By the mid-2020s even Londoners were noting, with some annoyance, that the global positive sense was crowding their older negative one.