Collgender is a term for multigender individuals who can't describe each one of their genders due to having so many. They have too many simultaneous genders to be able to describe each one individually. Instead, they may choose to describe them more as a collective, describe a few individual genders but not all, or not describe them at all.
History
Collgender was most likely coined by Pride-Flags on DeviantArt on August 18, 2015.[1]
Flag
The flag was designed by DeviantArt user Pride-Flags on August 18, 2015. It has no confirmed meaning.