You use self-same when you want to emphasize that the person or thing mentioned is exactly the same as the one mentioned previously.
例句
You find yourself worshipped by the self-same people who beat you up at school.你發現原來在學校里痛扁你的同一群人現在成了你的崇拜者。
英英詞典釋義
Adjective
1. being the exact same one; not any other:;
"this is the identical room we stayed in before""the themes of his stories are one and the same""saw the selfsame quotation in two newspapers""on this very spot""the very thing he said yesterday""the very man I want to see"