Christ was never called Yah, but our Holy Father is called by that name.
Yes, Paul does call him by that name according to his understanding of a certain Psalm which he quotes from and expounds.
Psalm 68:18
18 You have ascended on high, you have led captivity captive, you have brought gifts for men: yea, so that even among those turned away, Yah Elohim might dwell!
Ephesians 4:4-15
4 One body, and one Spirit, even as you also were called in one expectation of your calling:
5 One Master, one faith, one immersion:
6 One Elohim and Father of all, who is over all, and through all, and in all.
7 But unto each one of us was the grace given according to the measure of the gift of Meshiah.
8 Wherefore he says, "When he ascended on high, he led captivity captive, and gave gifts unto men." Psa 68:18
9 Moreover this, "he ascended", what is it but that he also descended into the lower parts of the earth?
10 He that descended is the same also that ascended far above all the heavens, that he might fill all things.
11 And he gave some to be apostles, and some to be prophets, and some to be evangelists, and some to be pastors and teachers:
12 For the perfecting of the holy ones, unto the work of ministering, unto the building up of the body of Meshiah:
13 Until we all attain unto the unity of the faith and of the knowledge of the Son of Elohim, unto a full grown man, unto the measure of the stature of the fullness of Meshiah:
14 That we may no longer be babes, tossed to and fro and carried about with every wind of doctrine, by the sleight of men, in craftiness, after the wiles of error:
15 But speaking truth in love, may grow up in all things into him who is the head, Meshiah:
Moreover this Meshiah Yah Elohim is the same you call Christ in your thread title. :chuckle: