Starting centered from the back of the neck, the two ends of a long strip of cloth cover the breasts, come together to cover the pubic area, go under and back to cover the groin, then up and around to tie off in the front.
Almost like a mankini made famous by Borat.
Not a joke answer, that’s what you describe.
You describe a form of what in the usual marketing speak is often sold as a “slingshot”, said qualifier then applied according to type of garment: slingshot swimsuit (beach), slingshot teddy (bedroom).
Image searching those two terms is most probably NSFW but not a bad way to spend a couple of minutes. 
Close, but unless I’m misremembering the version I was thinking of ties off around the waist.
As a side question, is there any man at all who doesn’t look gay in a mankini?
Nm
Sounds like it’s shaped like a moebius strip or a klein bottle - so “klein booty”?
Me.
I’d look tragic, not gay.
I’d expect better fashion sense from a gay man.
Having done the research, it appears these are called sling shots when marketed to women and v-style when marketed to men.