I think this is the first word with this suffix when proceeding in an alphabetical fashion. At least, it is the first that I have noticed. And I did not think that it would be such an old word; a single reference from 1852 illustrates the usage. I suppose it should not have surprised me had I thought about it a bit more. Why shouldn’t “-ish” be an old suffix?
acutish, a.
Somewhat acute.
Neh 