처녀작이 · 처녀작을
first work, maiden work, debut work
Example
그의 처녀작은 출간되자마자 큰 인기를 얻었어요.
His first work became hugely popular as soon as it was published.
Word parts
처녀 'maiden' + -작 'work': an author's very first published work.
Good to know
데뷔작 is the more modern, neutral word for the same idea.