I replaced my husband's underwear with Real-Fit briefs, and that's what I call them: your briefs. He has not said a word, just makes sure he changes them twice a day. Now, if I could get him to stop dribbling all over the floor...... (Even when he sits down to pee, he manages to spray between the seat and the bowl.)
I used Depends for my husband when he first became incontinent. I ALWAYS called them his underwear and never used the word "diapers" when referring to them as I wanted my husband to maintain his dignity. And even as his dementia progressed and he became bedridden and under hospice care, in which they only provided the tab type diapers, I continued to call them his underwear when referring to them. A lot of the ladies in my support group just replaced their husbands underwear with Depends so that when their husbands went to their drawer to get their underwear that was their only option for them and it made the transition easier for all involved.
Nothing really 'passes' for men's underwear in the realm of incontinence briefs, let's face it. Depends pull ups is the closest you'll come, I suppose. "Diapers" have tabs and most adults grimace at the mention of that name. Pull ups or incontinence briefs have a better sound to them, in most people's view. If you replace your father's underwear with pull up's, and he has dementia going on, he may not give you a hard time about wearing them. That's what many of us find here on the forum with our parents or loved one who suffers from dementia.
And even as his dementia progressed and he became bedridden and under hospice care, in which they only provided the tab type diapers, I continued to call them his underwear when referring to them.
A lot of the ladies in my support group just replaced their husbands underwear with Depends so that when their husbands went to their drawer to get their underwear that was their only option for them and it made the transition easier for all involved.
Good luck.