Graham has a post up (here: my linker isn’t working: http://doctorzamalek2.wordpress.com/2010/12/26/1970s-bonding-the-den/) about the 1970s and dens and it just so happens that I’m in a bona-fide den while this blizzard goes on. (My father in law was kind enough to clear it out for me to do grading here.) But that’s clearly a word from the 70s and 80s. Then the den became an “office” (very 80s “professional”—which means having the same stuff but without the shag carpet) and now, having lost all sense of irony from its first use, we have (or at least my brother has, along with millions of others) the “man cave” (the shag carpet can come back).
Let’s see how this works on the other side for women for “personal space”: 1950s: the kitchen; 1970s: the kitchen; the Aughts: the kitchen… (when not in the “family” room)