sive induatis femoralia - the word Femoralia refers to drawers or something that wraps on the thighs of the underclothing...this is not an endorsement of Trousers or Pants. Since there really is no word for Trousers or Pants in Latin as we understand it, this is used.
In addition, St. Thomas, never says cultures are permitted to wear what they wish, but that, in necessity or to hide oneself.
Lastly, pants or trousers are not evil-in-themselves -- like Abortion is.
However, if for medical reasons, an under-garment to keep warm, homelessness, or a great necessity it is NOT permitted to wear clothing that represents a man.
Men open their legs, women don't.
Men were built for manual-labor not women.
Imagine a woman trying give birth with pants on? Much easier to lift up a dress.
And, even if a woman wears a short mini-skirt -- she is sinning (unless necessity prevails or some other great reason) however, she is more feminine than a woman that wears pants.
What a small sacrifice for Heaven.
If it is hard enough to be pure and chaste seeing women wear dresses, how much more pants and trousers that usually are very tight and reveal the buttocks and the vagina.
Only what a husband should see.