This is the 11340th most frequent Korean word.
김옥길
"김옥길" is a Korean proper noun, commonly used as a personal name.
In this sentence, "김옥길" is used as a proper noun referring to the name of a known individual, Kim Ok-Gil.
김옥길은 훌륭한 교육자였다고 알려져 있다.
Kim Ok-Gil is known to have been an exceptional educator.
Here, "김옥길" is also a proper noun representing the sender's name in the context of receiving correspondence.
김옥길로부터의 편지를 받았는데 내용이 감동적이었다.
I received a letter from Kim Ok-Gil, and its content was moving.
In this sentence, "김옥길" denotes the person whose philosophical ideas the students are studying.