Libellula comes from the Latin for little book and refers to the open wings spreading like the pages of a book. Forensis is "of the forum or market place", referring to those that may enter town during their early adult life. This is a bit of an odd name as many will flit about settled areas when foraging if that is where the bugs are! Mind you, the same goes for the genus name -most of the dragonflies open their wing like a book and in many languages (including French, Spanish, Italian and Romanian) the word for dragonfly is some derivation of libellula.
The eight-spots are the total large black blotches that you can see here.