गुह्यतम
guhyatama
The most secret or most intimate teaching, given with affection to a dear listener.
Guhyatama means "most secret". In the Gita the word comes around the final counsel. In verse 18.63 Lord Krishna says he has told knowledge more secret than the secret, and in verse 18.64 he is about to speak again his supreme word, the most secret of all.
"Secret" suggests something hidden away. But the reason is given in the same breath: "You are very dear to me; therefore I shall tell you what is for your benefit." So the secrecy is that of intimacy. It is the word spoken to the closest listener, with affection, for their good.
The call to refuge comes within this word. So in reading guhyatama, look less for a mystery to be solved and more for the feeling in which it is spoken: closeness before command.
The order and sense of this counsel become clearer when read with refuge.