When the people of Israel came out of the Red Sea and saw God destroy the Egyptian army, they burst into praise. In the first lines they called God My strength and song. Those lines and this name of God are repeated twice in the Old Testament because it was such a momentous occasion.
My strength and song in Hebrew:
Strong’s Concordance numbers: 5797, 2172
Bible references: Ex. 15:2; Ps. 118:14; Isa. 12:2
The Lord is my strength and song,
And He has become my salvation;
This is my God, and I will praise Him;
My father’s God, and I will extol Him. (Exodus 15:2)