Jah

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representing Hebrew Yāh, abbreviation of Yahweh. The current use was popularized in the mid 20th century.

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etymonline

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Jah (n.)

1530s, a form of Hebrew Yah, short for Yahweh "Jehovah" (see Yahweh; also see J). Used in some English bibles. Cognate with the second element in hallelujah and in Elijah.