'Known' in the Bible

Will you steal, murder, and commit adultery, and swear falsely, and burn incense to Baal, and walk after other gods that you have not known,

I will scatter them also among the nations, whom neither they nor their fathers have known; and I will send the sword after them, until I have consumed them.

therefore will I cast you forth out of this land into the land that you have not known, neither you nor your fathers; and there you shall serve other gods day and night; for I will show you no favor.

The prophet who prophesies of peace, when the word of the prophet shall happen, then shall the prophet be known, that Yahweh has truly sent him.