Zilliogender is a multigender, that is a subset of mathgender, in which one feels as though they have, experience, or encompass a zillion genders. It should be noted that a zillion is not a real number and simply refers to "an indeterminate, very large number", presumably a number larger than a trillion or quadrillion (two of the largest, commonly known numbers) It is similar to billiogender, centilliogender, kilogender, platilligender, and trilligender. It may also be considered a subset to pangender.
Zilliogender was coined on July 31, 2018 by Tumblr user arco-pluris. The flag was designed by Fandom user Reign of the breadsticcs on March 10, 2021.
There are 15 individual sections on the flag to represent the supposed 15 zeroes and up in the number zillion, and the pi symbol represents the seemingly unending complexity and vastness of zilliogender.