In part 3 of Jack Kerouac's On the Road, the narrator is trying to talk to a pretty country girl at a bus station. He describes her as "dull" when he finds out that her life experience is very limited and that "her heart was not glad". He then asks what she does for "fun" and continues:
I tried to bring up boyfriends and sex. Her great dark eyes surveyed me with emptiness and a kind of chagrin that reached back generations and generations in her blood from not having done what was crying to be done--whatever it was, and everybody knows what it was. "What do you want out of life?" I wanted to take her and wring it out of her. She didn't have the slightest idea what she wanted.
I was very struck by the deliberate mismatch here between the mystery of "whatever it was" and the fact that "everybody knows what it was". But I certainly don't know what "it" was, and the book never tells us. What is "it", and why does Kerouac imply it is at once both mysterious and obvious?