뭘요

what?, not at all, it’s nothing

→ 뭐+를+요
뭘 Accusative + 요 Polite speech
pronoun · formal Rare #22,838
what? A polite, conversational way to ask “What?” or “What do you mean?”
KO: 뭘요? 무슨 일이에요?
EN: What? What’s the matter?
not at all, it’s nothing A modest response that plays down a compliment or thanks.
KO: 뭘요, 별일 아니에요.
EN: Not at all; it was nothing.

뭘요, 무슨 일 이죠?

What, what's going on?

— 멀홀랜드 드라이브 (2001)

뭘요, 아버지?

What is it, Father?

— 하얀 리본 (2009)

뭘요?

What?

— 오펜하이머 (2023)

내가 뭘요?

What am I?

— 포풍추영 (2025)

사모님, 그 정도로 뭘요

Ma’am, it’s really nothing.

— 마루 밑 아리에티 (2010)