The full form of FKK is frei-körper-kultur
This acronym is used to represent the German phrase “frei-körper-kultur.” This phrase translates to English meanings “free body culture.” It is typically a phrase you will see pictured on signs for clubs, saunas, and beaches where it is acceptable to swim, sunbathe, or participate in other activities without wearing clothing in public areas.

Origin of FKK
The German phrase that this acronym represents has been used since at least 1898. It defines a sub-culture in the country of Germany which people believe it is acceptable to be nude and perform daily activities in this matter to be closer to nature. The choice to be nude and participate in these activities or live in this manner has nothing to do with sexuality. It is simply done so that people can be closer to nature and completely free.

Other Meanings
There are quite a few other things that this acronym can represent. Some of these are “Fehrbelliner Karneval Klub,” “Feuer Knueppel Krug,” “Flickr Klub Karlsruhe,” “Fauler Kiffer Klan,” and “Fort Knox Kentucky.” These are just a handful of the things that can be represented by this acronym. There are several more, but too many to list them all here. However, most times the acronym is mosty used to represent the phrase mentioned above.

Conversation Examples
A text message exchange between two friends.

Friend 1: Did you enjoy your trip to Germany?
Friend 2: I did, but I have to tell you something funny that happened. We went to this beach and we are walking down in our bathing suits. We saw this sign in German with FKK printed on it. We didn’t know what it meant so we keep walking down to the shoreline and all of a sudden we look up and everyone is naked!
Friend 1: No way!
Friend 2: Yeah, apparently we learned later that the FKK stands for a German phrase and indicates that the area is for nudists. The look on my dad’s and brother’s faces was priceless.
Friend 1: I bet!