YHWH and Jehovah: Same? Different? Where's Jehovah Come From?

I received a number of comments on my recent posts about whether Jesus was Yahweh (Hebrew: YHWH) in traditional Christian thinking/theology.  And a number of people have wanted further explanation of the name.  In particular: how does it relate to "Jehovah"?  In fact, where does the name "Jehovah" come from?   And is it in the New Testament? Read by Sam Devis