Currently, we have anime-history, manga-history, and game-history on the main site, with 17, 3, and 1 questions, respectively. We've also had other history tags at times, such as cosplay-history on this question, which is now tagged (somewhat incorrectly) as anime-history. In principle, we could also get light-novel-history, visual-novel-history, voice-acting-history, and presumably others.
Is there a benefit to having separate tags for these? I can see why anime-production and manga-production would require somewhat different knowledge to answer in, but in the case of history I think the same people would tend to be experts on both, and there's little benefit to splitting them up.
As such, I propose merging these three tags into one history tag which covers all questions about history within the context of anime and manga. anime-history and manga-history could be made synonyms of this so that newcomers have an easier time finding this tag.