Plumerian was coined by Tumblr users Care-A-Lots and Genderless-Gibberish on August 4, 2018. The term comes from the plumeria flower.
The flag was designed by nova-is-hella-cute (now known as hella-cute-and-fruity) on August 7, 2019. The first three stripes come from the colors of the plumeria flower. The white stripe represents the absence of gender. The green comes from the agender flag.
The updated version was posted January 5, 2020, also by hella-cute-and-fruity. The stripe meanings are the same as before, but the hues are adjusted to be higher contrast and more distinct.