Secretary \SEK-ri-ter-ee\ , noun;
1. A person employed to handle correspondence and do routine work in a business office, usually involving taking dictation, typing, filing, and the like
Today is Secretary's Day. Okay, it's actually Administrative Professional's Day, but you know what I mean. Secretary is first attested in 1387 as "person entrusted with secrets" from Middle Latin secretarius ("clerk, notary, confidential office, confidant") based on Latin secretum ("a secret"). The Latin word is actually a compound of se- + cernere. Se- means "without, apart" or "on one's own" from Proto-Indo-European *s(w)e-, which is the third person pronoun and the reflexive marker. Cernere means "separate" and comes from the Proto-Indo-European root *krei- ("to sieve, discriminate, distinguish").
I think that the transition from "secret keeper" to our modern idea of a secretary (or administrative professional, let's be p.c. about it) makes a lot of sense if you watch Mad Men.