The text I questioned is, indeed, in the FAQ, under the "How to Join Ecency" section. It states:
Your password is your master key to your account.
The way we normally talk about security on Hive is that there is a "Master Password" from which four Key pairs (public and private) are derived: Owner Key, Active Key, Posting Key, and Memo Key. There is no "Master Key," per se. But then, you didn't capitalize it, either, as if it were an official term! 😉
HOWEVER, I understand that "Master Password" would be confusing to most Internet users, very true. So, perhaps it's best to leave it as is, I am not sure. You have to do what you feel is best for your user-base! Thank you for your response! 🙂