For centuries, women in one Chinese county wrote in a script men couldn't read

In Jiangyong County, Hunan, women barred from formal education developed Nüshu, a phonetic script of several hundred characters, passed down secretly from mothers and grandmothers to daughters. They embroidered it into cloth and wrote it into 'third-day letters' given to brides three days after their wedding, expressing grief, friendship and hope. It's considered the only writing system in history created and used exclusively by women.

— Wikipedia contributors, Nüshu — Jiangyong County, Hunan, China