A pubic hair piece. A toupee for the pubic area/genitals. In the 1700’s when mercury was used to treat sexually transmitted diseases (Gonorrhea or Syphilis) one of the side effects was the loss of pubic hair. To disguise this condition, that was not cured by mercury, a Merkin was employed.

The wearing of a g-string, thong, or the like - the wrong way around. Either back-to-front. Or, more often, sideways. Often occurs when getting dressed while intoxicated.