였다는

was (that)

→ 이다

였 Past tense + 다 Plain declarative ending + 는 Topic marker

auxiliary · past tense Rare #31,117

was (that) Used to mark a clause meaning “that someone or something was …”.

KO: 그가 의사였다는 걸 몰랐어요.

EN: I didn’t know that he was a doctor.

Conjugation of 이다

내가 형편없는 남자친구 였다는 거 알아

I know I was a terrible boyfriend.

— 빅 식 (2017)

톰이 아동 심리학자 였다는 것을 난 몰랐어.

I didn't know Tom was a child psychologist.