the etymology of an author

In exploring the question "what is an author?", one of the most interesting points of discussion for me is whether or not an author must produce written works. One can conceive of the "author" of a piece of art, or the "author" of an idea, but why is it that authorship is most commonly associated with writing? How did author and writer come to suggest the same idea (although there are some clear differences in how we use these terms)?

I decided to search for the etymology of the word author, and according to the online etymology dictionary:
"c.1300, autor "father," from O.Fr. auctor, from L. auctorem (nom. auctor) "enlarger, founder," lit. "one who causes to grow," agent noun from augere "to increase" (see augment). Meaning "one who sets forth written statements" is from c.1380. The -t- changed to -th- on mistaken assumption of Gk. origin. The verb is attested from 1596."

From the Old French, we can understand author to mean "father," while Latin gives us the idea of "enlarger," "founder," or literally "one who causes to grow." We see from this site that the meaning of author as "one who sets forth written statements" emerged around the year 1380, which predates the invention of the printing press by 60 years. It is also interesting to note that enlarger is not a commonly imagined synonym for our modern use of the word author. In class, we discussed words such as poet, writer, creator, inventor, artist, journalist, composer, and scribe as substitutes for the word author. "Enlarger" would have been a questionable addition to that list. While "founder" still rings true for our conception of an author as an inventor or originator, and while "father" lends itself to our idea of author as creator, "enlarger" seems to have lost its' original meaning. I wonder what the word enlarger might have indicated in the Roman context. In what sense is an author an enlarger? What exactly does an author increase, or cause to grow? Ideas? Understanding? Literal words on a page, as they expand in length? If an author is a creator, who creates something out of nothing, than does he also inherently enlarge what he has created into something worthwhile, enlightening, and edifying? Is an author one who causes our minds, our points of view, to broaden? In this sense, is that the author's responsibility?

If we focus upon the idea of an author as an enlarger, that meaning does not necessitate that the author write something. Nor does the idea of a founder or father, for that matter. I would be interested in exploring more of the history behind the development of the word author and exactly how it came to mean what it means for us today in our historical and cultural context.