[Nimhfree]

You can try from Blizzard_TradeSkillUI.lua:

			--[[ Parent categories ]]--
			local categories = { C_TradeSkillUI.GetCategories() };

			for i, categoryID in ipairs(categories) do
				local categoryData = C_TradeSkillUI.GetCategoryInfo(categoryID);
				info.text = categoryData.name;

The name is localized. However, it appears with my brief testing that you need to have opened the Blizzard panel up first before C_TradeSkillUI API actually returns non nil.