I am looking for terminology to describe a common collective social behavior. Is that question appropriate for this site? I could also ask on English, maybe, if I phrase it carefully. There's a sociology tag on Philosophy too but it does not seem appropriate.
First of all, welcome at CogSci.SE. Recently we've been having a rather extensive discussion about what is on- and off-topic here. As you can see in the linked meta-post, sociology is on topic. To quote the post:
We decided to welcome any cognitive science, in line with the definition of Wikipedia. This includes any field which tackles the mind or its processes (behavior), including animals. E.g., Human-Computer Interaction, Neurobiology, Applied Psychology, Social Psychology, Sociology, Neuroinformatics.
Please, ask your question thus :)