Nymboy - Also known as abinboy. This refers to a boy who is completely removed from the gender binary. It’s a kind of boyhood that lacks ties to the gender binary, which includes a relationship with binary boyhood, manhood, maleness, cisness, male-alignment, binary masculinity, and most other widespread connotations of boyhood.
Nymgirl - Also known as abingirl. This refers to a girl who is completely removed from the gender binary. It’s a kind of girlhood that lacks ties to the gender binary, which includes a relationship with binary girlhood, womanhood, femaleness, cisness, female-alignment, binary femininity, and most other widespread connotations of girlhood.
The “nym” in both genders refers to the fact that the user is using boy/girl as homonyms. The gender that they call boy/girl is separate from the binary genders despite it having the same name, making it a homonym.
Nymboy was coined by @/xenoleaf, found here. Nymgirl was coined by u/hiitsyaz on Reddit, but I couldn’t find the original post.