This porn video tag, "you-cock," is likely a phrase used in a specific context during adult videos. The term "you" refers to the viewer or participant, and "cock" is slang for male genitalia. So, "you-cock" could mean something along the lines of "your cock" or "the viewer's/participant's cock." This phrase might be used in a video when talking about the viewer's involvement or excitement related to their own male genitals