The idea that role playing involved a property called "immersion" occurred to the early adopters of the 1970s fairly early. The earliest explicit use I've found was that of Pieter Roos, as shown in this excerpt above from The Wild Hunt #15 (1977), where he identifies it as the overall goal of playing RPGs. Before the end of the decade, calls to "immerse yourself" began to appear in games and modules published by TSR. The Elusive Shift pays particular attention to the uptake of "immersion" as a term because of its relationship to how people in the 1970s understood the nature of role playing.