The phrase "first gay" in the context of a porn video tag means that this specific content features a homosexual encounter or experience for one or more of the individuals involved. It indicates that this might be their first time engaging in same-sex activity, or it could be referring to the scene being the first gay scene in the series or collection. This tag is used to specify that the video contains gay content and may appeal to viewers who enjoy watching or supporting novice experiences within the genre.