The Android search dialog below is displaying suggestions I supply using my own content provider (aardvark, another, apple). Below that list is a second list (about, all, …) which I do not want. What is the technical term for that second list, and why is it shown? How can I suppress it?

The second list is an auto-completion feature which has nothing to do with your search dialog. It is a keyboard feature which suggests common words from a dictionary. It can be enabled or disabled in the keyboard preferences but the choice is up to the user.
Generally it is disabled by default but on the emulator the default settings are sometimes different (because it emulates a development device, not a production device). It can also change between languages.
If you are sure that these suggested words are useless then you can disable this feature by adding
android:inputType="textNoSuggestions"to your<searchable>tag.