Jehovah is a Latinization of the Hebrew, one vocalization of the Tetragrammaton (YHWH), the proper name of the God of Israel in the Hebrew Bible.
The consensus among scholars is that the historical vocalization of the Tetragrammaton at the time of the redaction of the Torah (6th century BCE) is most likely Yahweh. The historical vocalization was lost because in Second Temple Judaism, during the 3rd to 2nd centuries BCE, the pronunciation of the Tetragrammaton came to be avoided, being substituted with Adonai ("my Lord"). The Hebrew vowel points of Adonai were added to the Tetragrammaton by the Masoretes, and the resulting form was transliterated around the 12th century as Yehowah. The derived forms Iehouah and Jehovah first appeared in the 16th century.
"Jehovah" was popularized in the English-speaking world by William Tyndale and other pioneer English Protestant translations such as the Geneva Bible and the King James Version. It is still used in some translations, such as the New World Translation and Young's Literal Translation, but it is does not appear in most mainstream English translations, as the terms "Lord" or "LORD": used instead, generally indicating that the corresponding Hebrew is Yahweh or YHWH. :5