Fact isn't as fun as fiction. They actually looked like uncircumcised dicks sticking off their face. That protrusion was to protect them from breathing in bad air "miasma" and filled with herbs. Also had absolutely no effect against the black plague since it was spread by flea bites. Being covered head to toe might have mitigated it more than the silly mask.
Sorry to kill the fun, just bothers me that this got so warped by pop culture into some cool ass crow mask.