Originally Posted by Fausset's Bible Dictionary

Yahweh
(See JAH; JEHOVAH.)

Originally Posted by Fausset's Bible Dictionary

Jah
Condensing in one emphatic syllable all that is implied in Jahveh (or Yahweh), the true pronunciation of Jehovah (Ps 68:4); first in Ex 15:2 (Hebrew). Often in names, as Eli-jah. Only in poetry: Isa 12:2, "Jah (or Yah) Jehovah is my strength and my song"; (Isa 26:4) "in Jah (or Yah) Jehovah is the Rock of ages." The union of the two names expresses in the highest degree God's unchanging love and power. Hallelu-Jah (or Hallelu-Yah) is "Praise ye Jah (or Yah)". Ps 89:8, "O Jehovah, God of hosts, who, as Thou, is a strong Jah (or Yah)?" the emphatic concentration of the name "Jehovah." The spirit impressed with a sense of God feels the need of repeating frequently that name in which His being is comprehended (Hengstenberg).