Mathematical sign language: https://aperiodical.com/2019/04/mathematical-sign-language-interview-with-dr-jess-boland/
Hearing-impaired eletrical engineering researcher Jess Boland discovered that weren't enough technical terms in British Sign Language to cover the mathematics she uses in her work, so she's been creating new ones as well as promoting the ones BSL already had. Katie Steckles interviews her for The Aperiodical.
(@aperiodical has a Mathstodon account but they're letting it go stale instead of promoting their new posts...)