Origin of Cheminformatics seems to be originated from Obernai declaration that states use of the word cheminformatics instead of chemoinformatics. But there is no single document that states it! Even more this declaration use chemOinformatics term!
Some funny notes from molinspiration site:
Date: Fri, 17 Oct 1997
From: Wendy Warr Subject: Re: Cheminformatics/Two new refs. I wonder if any of the sources define this awful neologism ("chemoinformatics" or "cheminformatics"). Does it really differ from "chemical information" or "computational chemistry". More...from Endy Warr About two years ago, many people (including myself) considered that "cheminformatics" was a nasty neologism. My survey this summer shows that it is now an established discipline, although the tasks involved, and even the name of the discipline, are not clearly defined yet. "Cheminformatics" was preferred to "chemoinformatics" by most respondents. More interesting about Google Ngram comment from the Dalke Scientific blog. More specifically, if you search for "cheminformatics" you'll see "About 6,960,000 results". Try to go to item 900 and you'll get the message:In order to show you the most relevant results, we have omitted some entries very similar to the 654 already displayed."Chemoinformatics" returns "About 96,500 results". Almost an order of magnitude less! But try going to the end of those and you'll see:In order to show you the most relevant results, we have omitted some entries very similar to the 671 already displayed.Shaky indeed!
So, my conclusion is the choice was made by some top molecular modeling people, highly connected to Internet communityand the final line was made when Journal of Cheminformatics appearred. From my point of view, chemoinformatics is more correct from grammatical point of view, but the world have some rules.