What does “(any sword)” mean in terms of Magic Items?

In the Dungeon Master’s Guide section for Magic Items (Chapter 7), a lot of items have a requirement that says (any ___), specifically weapons and maybe armor if I remember correctly. For example, Flame Tongue says: “Weapon (any sword)”. Is this just to classify what the Item can be, or can you use another Magic Item in this place? Personally, I think a Vicious, Flame Tongue, Dragon Slayer, Vorpal Sword would be dope, but I’m not sure if that would work.