Jehovist or Yahwist is the name given in higher Biblical criticism to one of the postulated authors of the Hexateuch. He is identified by his use of the divine name Jehovah or Yahweh as opposed to Elohim, used by the author of the first chapter of Genesis.
The word Yahwist was first used in 1753 by the Catholic physician, Jean Astruc (1684 - 1766) in his book Conjectures sur les mémoires originaux dont il paraît que Moïse s'est servi pour composer le livre de la Genèse for the writer of that portion of Genesis that was likely written by a different author than the first chapter. Over time it evolved into the German Jahvist, then the English Jahwist, then the modern English Jehovist, in relation to the Latinized version of the name of the Hebrew God, rendered "Jehovah".
Astruc's use of the word "Jehovist" in his formation of the documentary hypothesis apparenty comes from his intent to describe the writer of the document that came to be known as "J" (for "Jahwist", 1822, Frederick Bleek; "Jehovist", 1853, Hermann Hupfeld), as one who used the name of Jehovah in his writings. It has been extended to anyone who uses the word "Jehovah" as the name of God, whether in worship or in Biblical transmission (writing or translation).
Later the term was used openly in regard to worshippers of the Deity. Afterward, the term came to be used to indicate a supporter of the translation of the tetragrammaton as "Jehovah", and those who cling to its pronunciation as "Yahweh" as "Yahwists".