A Koan (公案) is a concept from Zen Buddhism. Zen made its way into pop-culture (or at least the popular counter-culture movement) in the US in the 1960s via several writers of the Beat Generation. Project MAC at MIT was founded in the early 60s (Gerald Sussman started there in '64 I think)? So a number of faux Koans were in circulation in the AI crowd by about 1970.