// interesting thought; we don't really have history on how jeanette && eleanor's names came to be; wether they were named after someone specifically or they just liked the names like with brittany's- ((here's the interview source for that brittany part:
I mean, I always thought that she was named after Jeanette Rankin (1st female US senator, elected in 1917), or it could be that Janice decided to find female names that were similarly antiquated by then to the boys'. Many names common 60 years ago are no longer really used in the US, but are moderately common in other English-speaking countries.
The minidocumentaries on the films have gotten the naming inspiration for the boys wrong to a some degree, so that Brittany clip may have also been the case. Also, my guesswork was based on 20th century famous ladies (pre-1950), and I just couldn't think of a woman in the public eye then named Brittany.