Quote, in fact, of basically all days, because a little meander through the Internet led me to the following fabulous entry in the OED:
Princeton, n. orig. and chiefly U.S.
attrib. Designating a form of male homosexual activity in which the penis is rubbed against the thighs or stomach of a partner.
1965 S. FRIEDMAN Totempole 265, I should have known..it would be the Princeton rub or nothing. 1969 W. H. AUDEN in N.Y. Rev. Bks. 27 Mar. 3/4 My guess is that at the back of his mind, lay a daydream of an innocent Eden where children play ‘Doctor’, so that the acts he really preferred were the most ‘brotherly’, Plain-Sewing and Princeton-First-Year. 1972 B. RODGERS Queens’ Vernacular 154 Princeton style,..fucking the thighs. 1980 Times Lit. Suppl. 21 Mar. 324/5 ‘Princeton-First-Year’ is a more condescending version of the term ‘Princeton Rub’; that is, coitus contra ventrem. 2004 D. BERGMAN Violet Hour iii. 105 He arrives there still a virgin, without even the benefit of the ‘Princeton rub’.
Hey, Yale, you think you can beat that?
Addendum: It’s interesting that the first citation is 1965. I would be very surprised if the expression weren’t in common usage long before that—see, for example, this fin-de-siècle gem dug up by Press Clubber David Walter.