You can find those previous search terms in the config.abz file. (Just open the file in Notepad, edit, then save.)
But I must admit that I would prefer to NOT have any search terms logged at all. (I think many of have had our share of red-faced moments when our online activity unexpectedly surfaces due to software logging)
Unfortunately there does not seem to be any way to disable Alt.Binz's search-term logging, or clear it without manually editing the config file.