en_tn/lev/18/19.md

to uncover her nakedness

Here the idiom "uncover the nakedness" of someone means "have sexual relations" with someone. See how you translated this idiom in Leviticus 18:6. Alternate translation: "to have sexual relations with her" (See: rc://en/ta/man/jit/figs-idiom)

the impurity of her uncleanness

This is the time every month when a woman bleeds from her womb. The words "impurity" and "uncleanness" both occur to emphasize how disgusting a man is to consider her nakedness at that time. (See: rc://en/ta/man/jit/figs-doublet)