No one actually uses „Klammeraffe“ in German. It’s just „at“ (English pronunciation – most of the time). I wonder how widespread the use of those alternative names for “at” is in other languages he lists.

In German „Klammeraffe“ is this weird, unwieldy nickname that used to be somewhat fashionable a long time ago (mid-nineties maybe, whenever many people where first confronted with email addresses). I remember it being used back then whenever people were explaining the internet in media (TV, radio, books), though I don’t think it ever got widely used outside that context.