Endogender is a gender for when one's gender is fluid or fluctuating, but is always at least somewhat related to a given gender(s). For example, one could always be at least partially masculine (endoboy or marfluid), feminine (endogirl or venufluid), androgynous (endoandrogyne or eafluid), or non-binary/neutral genders (endononbinary or eafluid) whilst being fluid in some way.
The term was coined by a unknown user on an unknown date, on or before August 14, 2015.
The endoboy and endogirl flags, as well as the alternate endoboy flag, were created by an unknown user on or before July 20th, 2016. They have no confirmed meanings.
The endoandrogyne, endoaliagender flag, and alternate endononbinary flag were designed by Kalliepride on Tumblr on July 30th, 2018. They have no confirmed meanings.
The alternate endogirl flag was designed by Pride-Flags on DeviantArt on August 14, 2015. The outer pinks represents femininity. The light lavender in the middle is a mix of pink, blue, and grey to represent those who shift to a partially feminine/masculine/genderless/non-binary feeling.
Endogender is from the Latin root “endo” meaning “within”.