Here’s a couple of impolite grammar forms ~
+(이)야: the impolite form of +이에요, +입니다.
이거 누구 책이야?
Whose book is this?
+니?: impolite interrogative.
지금 뭐 하니?
What are you doing now?
+아/어(라): impolite imperative sentence. 라 is often omitted.
+더라: impolite sentence ending which expresses a fact that is known by listening/seeing
내가 갔을 때 엄마를 밥을 먹더라.
When I went there, Mum was having a meal.