Continuity mistake: When Lolita begins to undress in front of Humbert, she is wearing her school uniform. Her shirt first appears tucked in, then out and then in again.
Continuity mistake: Lolita goes into Humbert's room and she is chewing gum. She then sits on Humbert's lap and sticks her gum on a piece of paper on his desk. A couple of shots later, she is chewing gum again.
Continuity mistake: After Lolita hugs and kisses Humbert goodbye before leaving for camp, the positions of his hands on her back change from shot to shot as he's lowering her back to the floor.
Continuity mistake: Just before Charlotte Haze gets hit by a car, when Humbert is preparing the drinks, the glasses are two thirds full. However, when he answers the phone, the glasses are only half full.
Answer: It could have been. Lolita might have used a relatively new term, and also how can one really pinpoint the first time a term was used? Maybe it was more mainstream in 1966, but kids could have been using the expression for several years.