YKIOK is an acronym that stands for "Your kink is okay." It originated on the Usenet newsgroup alt.sex.bondage and was often used in conjunction with the acronym IJNMK which stands for "It's just not my kink." These acronyms were created to give people a nonjudgemental way of communicating their kink preferences.
More About YKIOK
YKIOK serves as a declaration and a way for members of the BDSM community to affirm that, regardless of how strange a kink may sound to the ouside world, if it is consensual, there's no reason to judge. This view seeks to challenge the mainstream notion that some BDSM activities are morally, or even legally, wrong.