The hanky code isn't real and i'm increasingly convinced it never was. Like some mechanic had a grease rag tucked in to her pants at the bar after work and was like "oh yeah this means i'm in to left handed blonde librarians who have never heard the crow of a black cock and speach dutch" and everyone else got in on the joke and some poor out of towner passing by was like "holy shit i had no idea" and reported it to her friends as gospel through.