things refers to the program Things. Makes sense. There was no wiki on this, so I just stumbled on to it. Of the 6 questions tagged with things at least 4 of them give some specifics as to what "things" is.
things be turned into things-for-mac or at least something more descriptive like things-mac-application. My first thought when I saw the things tag was "what things?" which lead me to do some digging and put in a wiki edit request. Ultimately, the things tag is way too generic and has the possibility of being misused. It should be a synonym for the new tag or burninated.