While "hanky code" can go by many names (including handkerchief code, bandana code, or flagging), the term refers to a system of signaling your interest in certain sexual interests and fetishes … I could forgive it if this so-called yellow handkerchief had a defining moment in the film, but no. The handkerchief code (also known as the hanky code, the bandana code and flagging) is the wearing of various colored bandanas around the neck was common in the mid- and late-nineteenth … While chatting with Kolodny and Michelson, Matt brought up "the hanky code," a form of covert communication that some gay men used in the '70s and '80s to signal their sexual interests and … In the '70s, the handkerchief code gained popularity among gay men who were in search of casual sex. The Yellow Handkerchief: who came up with that?There is nothing stimulating about that title. In the '70s, the handkerchief code gained popularity among gay men who were in search of casual sex.