The word "Jehovah" appears in a lot of Christian hymns and worship songs. But did you know that the word itself originates from a mistaken, literal-phonetic translation of Hebrew letters? Here's the explanation...
The term tetragrammaton (from Greek τετραγράμματον, meaning "four letters") refers to the Hebrew theonym (Hebrew: יהוה)transliterated to the Latin letters YHWH. It is derived from a verb that means "to be", and is considered in Judaism to be a proper name of the God of Israel as indicated in the Hebrew Bible.
As Jews are forbidden to say or write the Tetragrammaton in full, when reading the Torah, they use the term Adonai. Christians do not have any prohibitions on vocalizing the Tetragrammaton; in most Christian translations of the Bible, "LORD" is used in place of the Tetragrammaton after the Hebrew Adonai, and is written with small capitals (or in all caps) to distinguish it from other words translated "Lord".
The original consonantal text of the Hebrew Bible was provided with vowel marks by the Masoretes to assist reading. In places where the consonants of the text to be read (the Qere) differed from the consonants of the written text (the Kethib), they wrote the Qere in the margin as a note showing what was to be read. In such a case the vowels of the Qere were written on the Kethib. For a few frequent words the marginal note was omitted: this is called Q're perpetuum.
One of these frequent cases was the tetragrammaton, which according to later Jewish practices should not be pronounced, but read as "Adonai" ("My Lord"), or, if the previous or next word already was "Adonai" or "Adoni", as "Elohim" ("God"). This combination produces יְהֹוָה and יֱהֹוִה respectively, non-words that would spell "yehovah" and "yehovih" respectively.
The origins for the composite term Jehovah, came from early English translators who transposed the vowels from Adonai to the Tetragrammaton, and read the word literally so that the Y in YHWH, was pronounced as a J in English, and the W as a V. Taking the spellings at face value may have been as a result of not knowing about the Q're perpetuum, thus resulting in the term "Jehovah" and its spelling variants. The Catholic Encyclopedia [1913, Vol. VIII, p. 329] states: "Jehovah (Yahweh), the proper name of God in the Old Testament." Had they known about the Q're perpetuum, the term "Jehovah" may have never come into being. Modern scholars recognize Jehovah to be "grammatically impossible" (Jewish Encyclopedia, Vol VII, p. 8).
The consensus of mainstream scholarship is that "Yehowah" (or in Latin transcription "Jehovah") is a pseudo-Hebrew form which was mistakenly created when Medieval and/or Renaissance Christian scholars misunderstood this common qere perpetuum; the usual Jewish practice at the time of the Masoretes was to pronounce it as "Adonai," as is still the Jewish custom today.
Curious about Jehovah's Witnesses? See this BBC page.