The story
*(Sex): By analogy with 69, a mutual oral sex position. *(Food): An antonym of 86 (“to temporarily remove an item from the menu”) via a reversal of the numbers.
Etymology from Wiktionary, CC BY-SA 4.0.
68
Today it means: A sex position in which one partner lays on top of the other, with their genitalia facing the other partner's head, in order for said partner to perform oral sex. Full definition →