To indicate this substitution in the Masoretic Text, the Masoretes added the vowel points from the word "Adonai" to the Sacred Name. Early Christian translators mistakenly combined the vowels of Adonai with the consonants of YHWH, producing the word "YaHoWaH." When theScriptures were translated into German during the Reformation (16th century), the word was transliterated into the German way of pronouncing it: the "Y" as the English "J", and the "W" as the English "V" -- or "Jahovah." In the early 17th century, the Scriptures were translated into English and the word was again transliterated, as "Jehovah."
This error has carried over into many modern (English) translations, but is now recognized as a translation error that was never used by the Jews.
by Micha F. Lindemans