Nanogender is group of gender identities that are a little of one gender and mostly another or others. These can be any genders. The “other” portion does not have to be only one gender. Under this definition, people who are nanogender have a nonbinary gender and are transgender .
'nan0girl,' as it was originally spelled, was first created by a truscum with a certain ableist-slur-containing-url to mock the identity demigender from hyaenahart’s list about compiling all gender and sexuality related pride flags, pride buttons, and pride scarves. It was reclaimed by captaintightpanties and boosted by both genderpunkrock and hyaenahart.--
The spelling “nan0girl” comes from the truscum post’s spelling of nanogirl as “nan0girl.” The spelling “NaN0girl” comes from the reclaimer, captaintightpanties. Both spellings are stylistic and have no change on the meaning, although according to captaintightpanties, “NaN means ‘Not a Number,’ and is a common error when programming if you try to call something that isn’t a number when the computer expects one” so using the “NaN0girl” spelling is a computer programming pun.