Well, since the thread seems to be going this way anyway...
Some very cool information here. I'd read some of 'Old is the New New' before but had no idea that Rob blogged on the history of RPGs.
Eliot, you are quite right about the RAND influence on poli-sci roleplaying games--the earliest article that I can find that actually uses the full phrase, from 1959, explicitly refers to a RAND study of 1958. Doing a little more digging, though, I've found that role-playing exercises were being widely discussed by the 1940s, but in rather different fields: sociometry and training, particularly nursing. Using role-playing for professional training was nothing new, of course--lawyers had been doing moot courts or similar exercises for centuries--but calling it role-playing seems to have been a new trend in the 1940s, in English at least. The sociometric role-playing seems to have been more along the lines of exploring social roles and group dynamics; it also seems to have been used for therapy, just as it is today.
Not sure, what, if anything, these earlier strains of role-playing have to do with RPGs as such; perhaps all they did was help popularize the term. Still, some of that literature might bear looking into by someone working on RPG theory--for instance, there seems to be some sort of analytical distinction between role-taking and role-playing, which conceivably could prove useful. Or not--I don't know enough to say.