Claude Mariotti wrote a nice post on the origin of the name Jehovah from the original YHWH as the personal name of God in the OT. Devout Jews avoid saying YHWH (pronounced Yahweh) out of honor for God, replacing it with either Adonai (Lord) or Hashem (the name). In the Hebrew Bible, the vowels from Adonai are transposed onto the divine name YHWH to remind the reader to say Adonai instead of Yahweh. This results in the Hebrew spelling YeHoWaH, although it is never pronounced that way. Modern English Bibles normally translate YHWH with LORD, Adonai with Lord, and Elohim with God.
What Dr. Claude pointed out that I was not aware of was that Jehovah was not used as a transliteration of YHWH until 1278 in the work of a Spanish monk.
Of course, you all immediately saw the significance of that date: If Jehovah was not in use during the 11th century (the first Crusade), then there is a mistake in one of the final scenes of the otherwise inerrant and inspired Indiana Jones and the Last Crusade. One of the clues to avoid the traps protecting the Holy Grail involved stepping on the letters in Jehovah to avoid falling to certain death. My faith in Steven Spielberg is now destroyed forever.