The name merely means “German Jews” — the roots go back to ancient Israel, a consequence of the “Lost Tribes” exiled to the frontiers of the Assyrian Empire.
Correct sir, except they are not of the tribe of Judah. So technically not Jews. They do have common ancestors but so do Arabs too. The descendants of Abram/Abraham. One by a concubine who was chased off, and one by his wife. His offspring with his Wife led to Jacob, I can’t remember who the next gen of his other “wife” was. He was also blessed, but less so.