Saying the Creator’s name is the revelation of the essence of the Creator’s four-letter name. Just like a seal imprinted in wax that leaves its mark, so does the Creator imprint His attributes in a person in an opposite form, and a person must correct them by making them resemble the Creator.
This is the mutual cooperation between the host and the guest when I, the guest, must imprint the desires of the host inside me. I must receive all the refreshments that He serves me so that He will be imprinted in me and carve His name in me, that is, the attitude of the host. When I enable that because I want His attitude, His attribute, to enter me, I receive it and thus connect to Him. The unity between the male part (the Creator) and the female part (the created being, the desire to receive) takes place as one enters the others, like a seal that that is imprinted in a soft pad leaves its mark.
Question: Why is it forbidden to say the Creator’s four-letter name aloud?
Answer: Saying the Creator’s name aloud means to reveal the Creator. The revelation takes place only inside a person, and he cannot convey his feelings to anyone else. According to the wisdom of Kabbalah, the word “forbidden” means impossible. You cannot reveal the Creator enough to pronounce His name. You can only absorb Him, perceive and receive His form that is totally imprinted on all of your matter, in all of your desire to receive, which leaves His mark (imprint) of His bestowal. This means that you should relate to His four-letter name Yud-Hey-Vav-Hey when you are advancing in the exact opposite direction, not from the top down, but from the bottom up.
In other words, the ten Sefirot of the Direct Light connect to the ten Sefirot of the Returning Light into one unique whole, and this state is called the goal of creation. However, unless His attributes have been attained, we mustn’t express His names. Even the name that is commonly used, like God—El is pronounced “Kel” in order to emphasize the respect we have for it. In our world, we also don’t call our father by name, but use the name “father.” This is a sign of respect for a person who is special to us, and thus we distinguish him from billions of other people. It is the same in spirituality.
From KabTV’s “Secrets of the Eternal Book” 1/28/15