I agree as far as 'interula', though I'm struggling to find many references to female underwear. It seems they had only the one word for undergarments for both sexes which is 'interula'.
Trousers is easy enough, and still familiar, 'Pantalones' or, for women, 'Pantalones de Senora'. 'Interula de senora' isn't good Latin but might better mean knickers which for me are definitively female.
I look forward to hearing the story.
Richard