Why is the journal of the Medieval Academy of America called “Speculum”: A device used to “examine hollow openings in your body, like your vagina, anus, ears or nostrils”
It's a word with multiple meanings, though admittedly the one you mention is the most common modern one. Presumably, given that it's a journal and about medieval studies, it's a reference to speculum literature: https://en.wikipedia.org/wiki/Speculum_literature
Yes, it is related to the usage there (and is listed on that page).
But here's the definitive answer from the publication itself:
"SPECULUM, this mirror to which we find it appropriate to give a Latin name, suggests the multitudinous mirrors in which the people of the Middle Ages liked to gaze at themselves and other folk — mirrors of history and doctrine and morals, mirrors of princes and lovers and fools."
From the preface to the first volume, linked at the top here:
EDIT: oh, perhaps the medieval genre of speculum literature: https://en.m.wikipedia.org/wiki/Speculum_literature