Absinthe is a green liquor that was the inspiration for a great deal of art and writing. And may have been responsible for Van Gogh cutting off his ear, so, you know, go easy on it.
Way back in the 20's, when Lovecraft was just getting started and freaks like Albert Fish prowled the streets, Absinthe was all the rage. Sure, you could smoke some opium or drink booze that wouldn't turn your liver into foie gras in a week, but nothing else had the mystique or nickname that Absinthe had. Absinthe was known as The Green Fairy, which sounds a bit weak, but they meant something along the lines of "Angel of Death" type fairy, so yeah, that is kind of bad-ass in retrospect.