Secretary
Is this from the root word "secret"?
Yes, the root of “secretary” is “secret,” which explains something about its original usage. Originally , a secretary was someone who knew all the secrets, and who handled confidential affairs for someone else.
While the modern usage of the word is quite different, a secretary still likely handles confidential matters. The word implies an assistant who “knows all the secrets.”
This also has political usage. The Secretary of State was originally known as “the state’s secretary,” meaning the person who knew the secrets of the state. It evolved from King’s Clerk, King’s Secretary, or Principal Secretary.
Additionally, there are many earlier usages in a religious sense: secretaries were entrusted with the secrets of God.
Why I Looked It Up
In The Swerve: How the World Became Modern:
[Poggio] had access, as the very word “secretary” suggests, to the pope’s secrets.
I also read a book called God's Secretaries about the creation of the King James Bible. In the sense of that title, the word uses both meanings: the translators transcribed things, certainly, but they were also responsible for conveying or guiding the secrets of the untranslated text.