Evidential past tense. Depends the verb, but it's usually verb-miş, which kinda sounds like 'misha' or 'mush' to my US ears. It's used when you haven't personally witnessed something. Like if you go outside and see puddles of water and a cloud that just passed and a rainbow, it clearly just rained but you didn't TECHNICALLY see it rain, so you say yağmur yağmış instead of yağmur yağdı if you had actually seen it.

So when you find a group of people gossiping, you just hear 'misha' 'misha' 'misha' 'misha' because they're all talking about inferred info, and I've heard it called the gossip tense.

And it's appropriate to note that I know all this second hand. I don't know any Turkish (besides Dur = stopsign from geoguessr), this is from my language nerd friend who speaks a decent amount, so I probably need to throw a -miş in here somewhere.