[dredmorbius]

Author stems from the same Latin root as authority, namely auctor, meaning "master, leader, author".

<https://www.etymonline.com/word/authority>

<https://www.etymonline.com/word/author>

So an author is one who creates, but also a "source of authoritative information or opinion".

Confusingly, authentic seems to have a different etymology, *autos "self" (see auto-) + hentes* "doer, being".

<https://www.etymonline.com/word/authentic>

So to authenticate an author as an authority derives three meanings from two separate roots.