the definition itself was actually created by a lost and now famous video of one guy and two girls putting a funnel in one girl's ass and pouring milk into it. the other girl then uses a straw and drinks the milk out of the other girl's ass. this video was around during the mid to late 90s and has since been lost. a lucky few may still have this video in their archive.
asscave was the original image of a woman's gaping asshole, scattered with nearly a dozen clitoral piercings, while her rosey red fingernail polish shined brightly on her hands that were spreading her ass. this legendary image was found years before goatse images started even appearing. a quick google image search for this name should produce results.
that's a disgusting picture, is it goatse? no it's asscave.