This association likely occurred because the older a single woman was, the longer she had been known as so-and-so spinster.

This is interesting, Dr. Bill, because I seem to recall from historical text, literature, and film, that there was a time in history where an elder never-married woman actually came to be referred to by that title in her community (Spinster Browne, for instance) as if were perfectly appropriate to address her that way...although, I'm not sure if someone would have actually used this to the woman in person.

dowager

2 : a dignified elderly woman

Hmmm...also a bit of a surprise, since I've always viewed this term as less than dignified, as in "some old dowager."

bachelor

later a young knight (before 1376)

I find this early meaning for bachelor intriguing.

Does anyone have any examples of this usage in period literature?