Nounself pronouns are a type of neopronouns that are derived from a noun to be used as a gender neutral pronouns. One can use any noun to turn into a pronoun and the sets can be themed around concepts that have nothing to do with gender, such as nature, technology, or abstract concepts. In that way it is similar to xenogenders, in which a person describes their gender by means of metaphorical concepts that have nothing to do with gender. Unlike most gender neutral neopronouns, which are intended to be used for all people regardless of gender, nounself pronouns are intended to be used by only a small number of people who feel that they express what is distinctive about themselves. It is also very similar to pocket genders, in that regard and many people who identify with a pocket gender also use nounself pronouns based on that gender.
History
Starting in early 2014, or late 2013, a community of non-binary gender people on Tumblr came up with the idea of "nounself pronouns" (some call these "otherkin pronouns," but not all using them are otherkin). Some of the earliest sets of nounself pronouns are the fairy themed set fae/fae/faer/faers/faeself, and the bunny themed set bun/bun/buns/buns/bunself. During 2014 and beyond, many sets of such pronouns were created, and many were adopted as the pronouns of particular non-binary people.
As of today the "fae" set is by far the most popular nounself pronoun set, with the "bun" set coming in a close second.