brew doctor can be really helpful here to make sure you don't need to cleanup, install, link, add to PATH, etc.

Other answers are accurate - it's likely your npm upgrade or reinstalling icu4c

This error can show up when installing php too - I ran into this error with brew install php on Mac OS Monterey 12 (which currently installs 8.4.14). Nothing worked for me though, I've tried everything.

Does anyone know if it's possible to install a version > 8.1 on this OS? I'm convinced it's not.