We don’t hear the word undergarment any more. We don’t need it any longer. When I was growing up you would hear it often. There would be phrases like:
You need to have on clean underwear, undergarment just in case you are in an accident.
Grandma would tell us to pull up our pants cause she could see our undergarment.
Her undergarment is showing. She must be wanting to look slutty.
Nowadays, it is normal to not only expose your undergarments, but to boast of the name brand, the color of your bra, or the femininity of your throng.
I guess discretion is no longer a moral virtue.