I had the pleasure of working with two of these. They did not give you the same quality of results that Google's website did. Utter garbage in a blue rack mounted case.
That's probably the same thing that you've encountered with the search appliance.
A word that shows up in the document and no others means it gets a very high score, vs "and" shows up in every document and thus doesn't score well for any
It's what Apache Lucene does which is what ElasticSearch uses under the hood.
Seems some form of wiki always has value inside a company?