The letter Y represents an intermediate between the celestial and the spiritual in man, especially in the heavens. Historically, it is closely connected to I and J in English, particularly when it's the initial letter in a word. When it's made with curves, a letter has something of the celestial in it. (Spiritual Experiences 5620, Doctrine Regarding Sacred Scripture 90)

88. To express the marriage of the Lord and the church, or in other words, to express the marriage of Divine goodness and Divine truth present in every particular of the Word, we find in many places the expressions Jehovah and God, or Jehovah and the Holy One of Israel, as though they were two entities, even though they are the same one. For Jehovah means the Lord in relation to Divine goodness, while God and the Holy One of Israel mean the Lord in relation to Divine truth.

The fact that Jehovah and God, or Jehovah and the Holy One of Israel, are mentioned in many places in the Word, and yet mean the same God, who is the Lord, may be seen in The Doctrine of the New Jerusalem Regarding the Lord 34, 38 and 46.