In the Old Testament various names for God are used. YHWH is the most celebrated of these; the Hebrews considered the name ineffable and, in reading, substituted the name Adonai [my Lord]. The ineffable name, or tetragrammaton [Gr., = four-letter form], is of unknown origin; the reconstruction Jehovah was based on a mistake, and the form Yahweh is not now regarded as reliable. The name Jah occurring in names such as Elijah is a form of YHWH. The most common name for God in the Old Testament is Elohim, a plural form, but used as a singular when speaking of God. The name El, not connected with Elohim, is also used, especially in proper names, e.g., Elijah. The name Shaddai, used with other words and in names (e.g., Zurishaddai ), appears rarely. Of these names only Adonai has a satisfactory etymology. It is generally not possible to tell from English translations of the Bible what was the exact form of the name of God in the original. In Islam, the name of God is Allah.