That's an interesting question, though it probably
is not known and maybe never will. Just as with
the origin of first words.
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That's all I found:
"A great deal of the scholarship on this question surrounds the question of the origin of alphabetical order. In the early days of the web, when I was interested in this particular problem, I had to consult (gasp!) libraries and live experts.

Now it is easy for anyone to proclaim expertise so an even more interesting question than what is the origin of alphabetic order is: how much of what you read on the web on this question is actually correct, or at least corresponds to the current scholarly thinking. It's a pretty problem for addressing this issue because, at least on the surface it is a small, self-contained, easy to state question.

In the early 1990's, the scholarly opinion was that the first interesting tablet relevant was that found at Ugarit around 1400 BCE and this is still cited by many webishes on this subject. Whether scholars still hold that idea or not I am clueless. The question of what the Ugaritic tablet might mean or what motivated/ the choice of order was highly speculative at that time and may still be. The most extensive primary literature was from the 1930s, but I think there is more since I last looked at it. Most likely, it is interesting to find out what is the status of claims from the late 90s of the Yale eygptologist John Darnell to the effect that there is 200 year older evidence for alphabetic scripts and ordering than the Ugarit tablet.

Posted by: Bob Morris | August 13, 2005 01:46 PM"

The alphabetical order for sorting information cannot be ascribed to anyone in particular.
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The first things ever to be sorted in an alphabetical order must be the words in a dictionary. But who created the first dictionary? We are clueless.

We can only get information like:
'The first Dictionary fascicle was published on 1 February 1884—-twenty-three years after Coleridge's sample pages.'

http://www.answers.com/main/ntquery
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I must say alphabetical sorting of information evolved over a long period of time rather than was invented by any particular person on a specific date, month or year.