From Don't Mess With a Seamstress:
They went to a special costume ball one Saturday night. She made Don a special dress.
Eva went as the man in top hat and tails, and Don was Dawn, her special lady, all decked out in feminine finery, wig, nylons, heels, jewels, makeup, and perfume.
Dawn's foundation garment controlled the shaping of her torso as well as supporting and shaping her bust line.
Eva explained to Don that his garment was what many socialites wore as a foundation. Dawn was to be her guinea pig. Don was quite distressed to think that he was her test case. He would have to stay dressed as a fancy lady for that full week.