If you meant a physical condition, you might be referring to (often called "Gamer's Thumb").
On platforms like Instagram, TikTok, or X (Twitter), this refers to the accidental "double-tap" or "like" on a post while scrolling. freemature thumbs
If "freemature" refers to a specific product or a very niche feature I missed, could you provide about where you saw it (e.g., an app name or a specific game)? If you meant a physical condition, you might