Beyond simply indicating past tense, what specific nuance does '-았/었었-' add when used in a Korean sentence, and how does this alter the interpretation of the event?

Beyond simple past tense, '-았/었었-' (double past tense) in Korean adds a nuance of anteriority, meaning the action or state occurred even further in the past than a single '-았/었-' implies. It indicates that the action is completed, and the state resulting from that action is also in the past, no longer relevant or continuing in the present. This often conveys a se....