I use a lot of fake slang. Most of it is intended to be similar to real world slang. In a lot of fantasy stories, the author indicates impossible/unrealistic things with italics or something similar with an aim to aiding the reading. I don’t like that because it breaks immersion; I want the characters to react to in-world things as if they’re just as normal as other in-world things. But I do understand that it makes life easier for the readers.
With regards to made up slang, hesh is similar to brother, though a bit more informal and close.
When Kog refers to getting hip action double-dirty, that’s not an extant boxing term, but it’s the sort of term people use in martial arts. Think baseball players calling pitches ‘stinky’ or ‘dropping bombs’ in striking.
The hungry plants have no analogue in the real world. They’re big things that look like Venus flytraps, but they eat trash. They will eat people if they can. Now a sober person, even sleeping, will probably wake up when the thing closes on them, but a drunk or injured person won’t. Hungry plants do have large, wet tongues they use to spread trash and introduce bacteria and other decomposing agents into a mouthful. They don’t have teeth, but they do have coarse hairs.
The words of power are a little different. They’re even more alien to reality, but in-world, they’re literal words. These are utterances that must be said with power, and they’re part of my world’s Cassirer magic system. In-world they’re not magic, though. They’re not sorcery. They’re verbal physics. Saying them with power means shouting, and their range is acoustic.