A person who is agender will either claim that they have no gender identity at all, or that their gender identity is neutral.
This is why it is often called “non-gender”, “genderless” or “null gender”, among many other names. It belongs under the non-binary umbrella term.
It has been proposed that “agender” should be an umbrella term itself, as “agendered” people describe very different experiences. Some feel like they have no gender at all, and do not wish to be associated with a gender.
Others feel like they have a gender, but said gender is neutral, not male or female or any other non-binary gender.
The concept was first defined in 1997, in the International Journal of Transgenderism, however, the term used was “ungendered”.
It was first in 2000 that an Usenet post claimed that the Christian God is “agendered”, which is the first evidence for the term on print.
The term was mentioned again on Usenet in 2005, explaining that cultures can have people who are “agender”.
In 2014, when Facebook opened up for non-binary gender options, “agender” was one of the 54 options.
The first person to be legally “agender” was a resident of Portland, Oregon, USA in 2017. The person took the case to court, and his request was accepted.