No idea where it'd originate from, but in central Utah it's common. A few others I've remembered include (similar to fer) your -> yer, our -> are, really -> rilly, prescription -> perscription, sale -> sell.
Robit is pretty funny, like a frog? Haven't heard anything like that.
A random YouTube search shows what I'd consider representative for the area, at least around my age, only a couple of fers though. Overall fairly "neutral". https://youtube.com/watch?v=k3IdMkc-aD4 Your sibling mentioned a similarity with Appalachian people, maybe some of it is a mountain thing, though if they had in mind anything like https://youtube.com/watch?v=Bn8O6Nx3C6w I don't really hear much similarity.
Robit is pretty funny, like a frog? Haven't heard anything like that.
A random YouTube search shows what I'd consider representative for the area, at least around my age, only a couple of fers though. Overall fairly "neutral". https://youtube.com/watch?v=k3IdMkc-aD4 Your sibling mentioned a similarity with Appalachian people, maybe some of it is a mountain thing, though if they had in mind anything like https://youtube.com/watch?v=Bn8O6Nx3C6w I don't really hear much similarity.