The original Hebrew and Aramaic parts of the Bible (as shown by the oldest of the Masoretic texts, circa 1100 A.D., and the Dead Sea Scrolls, circa 100-200 B.C.) certainly used the word "YHWH" (or "JHVH") for the personal name of God. This does appear around 7000 times. Modern English Bible translations usually render this as "Yahweh" (cf. New Jerusalem Bible) and olders ones often render it as "Jehovah". Most modern translations don't render it as a name at all, but as "LORD" or "God". Such translations do a disservice, I think, to the original texts.
There are no New Testament texts that contain any form of "YHWH", either in the Hebrew form or in translation. Thus, any translation that uses "Jehovah" or something similar in the NT, in place of "Lord" or "God ("kyrios" or "theos") is not being true to the text.
There is some evidence that the early versions of the Greek Septuagint version of the Hebrew bible used "YHWH" written directly in the ancient Hebrew letters. However, almost all extant manuscripts do not contain it, but use "theos" or "kyrios" instead.
By the time of Christ it appears that most Jews did not use "YHWH" in their worship, but used other words instead. This was due to a reverence for the divine name that perhaps went beyond common sense to the point that the name became more of a magical talisman than a useful name for God. It is virtually certain (according to most scholars) that by about 100 A.D. no Jew or Christian used "YHWH" in normal worship. All Greek manuscripts of either the NT or the LXX after about that date did not use "YHWH".
When the Jewish Masoretes, who ended up being the keepers of the Hebrew bible, added "vowel pointing" to their manuscripts beginning around the 7th century A.D., they generally "pointed" "YHWH" with vowels that were nonsensical in terms of regular Hebrew usage. Sometimes they used the vowels of "adonai" (Lord) and sometimes of "elohim" (God) and sometimes something else. It was understood that when the reader encountered the pointed "YHWH" when reading, he mentally or orally substituted "Lord". This was all due to the long established practice of avoiding pronouncing the divine name.
AlanF