G-string
noun
ˈjē-ˌstriŋ 
: an article of clothing that consists of a thin strip of cloth covering the genitals with the back portion made up of a string-like piece of fabric that passes between the buttocks and connects with a very thin waistband
Note: A G-string is typically worn as an article of underwear or swimwear or as part of the attire of a striptease dancer.
Word History
Etymology
origin unknown
First Known Use
1878, in the meaning defined above