“Jah” means Jehovah

Jah: the abbreviated form of Jehovah, used only in poetry. It occurs frequently in the Hebrew, but with a single exception, (Psalms 68:4) is rendered "Lord" in the Authorized Version. The identity of Jah and Jehovah is strongly marked in two passages of Isaiah-- (Isaiah 12:2; 26:4) [JEHOVAH].