It is generally thought that YAH is a shortened form of YHVH. This Name of God occurs about 50 times in the Tanakh. In Psalm 68:4 [5, H] this Name is particularly stressed. The Name YAH is also found in the construct word "hallelu-YAH," which means "you [pl.] praise the LORD," as well as in many Biblical proper names (e.g., Eliyahu).
The first occurrence of the Name YAH occurs in Exodus 15:2, where Moses and Israel sing a song regarding their deliverance from Pharoah's horsemen: