In the 1985 novel Footfall by Larry Niven and Jerry Pournelle I came across the following paragraph:
They took out identification cards. Clybourne glanced at them, but Jenny thought he looked at them superficially. He was much more interested in the visitors than in their papers. Doesn’t miss a detail. Joe Gland, thinks he’s irresistible.
Then a bit later:
They both act that way. Of course. Not Joe Gland, just a Secret Service agent doing his job.
From the context I understood this "Joe Gland" to mean something of a self-important, maybe vain man attempting to look good in front of a woman, but I wasn't entirely sure (it doesn't really make sense), so I checked in Google, and found very little: facebook profiles, the book itself, a tweet and a forum post; so I thought I'd ask it here.
What's a Joe Gland? I suppose it's US slang, popular primarily in the 80s or earlier, or maybe never really widespread. What does it mean, when it was first used, what's its etymology?