Tidings is an old-fashioned word for recent news. If someone says "I bring you good tidings!" it means they have information to share that you'll probably like.
Even though this word appears to be related to tide, tidings is actually thought to come from the Old English word tidan, which means "to happen." This term is a little unusual since it’s almost always in the plural form; you would never say, "I bring you a good tiding"!