Gendersharp refers to when one's gender feels sharp or more high pitched than normal.
Genderflat refers to when one's gender feels flat or more low pitched than normal.
Gendernatural refers to when one's gender does not feel sharp or flat, or is in between sharp and flat.
Gendersharp, Gendernatural, and Genderflat was coined on July 21, 2014 by no-bucks-for-this-doe on tumblr.
The flags were created on March 14, 2017 by Pride-Flags on Deviant-art.