Names of God and the Sefirot
“Most kabbalists integrated the biblical names of God into the system of the sefirot. Thus, for instance, the tetragrammaton–the biblical name of God written in four letters, YHVH, which in Hebrew, it is forbidden to pronounce–was interpreted as presenting the first sefirah, keter, in the almost-hidden little point above the first letter, yod, which represents the second sefirah, divine wisdom (hokhmah).
The first letter, he, is the binah, followed by the vav, which represents the number six, and thus relates to the six central sefirot from hesed to yesod. The last he represents the female entity, the shekhinah …
It can be stated that the system of the sefirot is viewed by most kabbalists to represent the hidden, secret name or names of God …
Kabbalists utilized the names that were used by pre-kabbalistic esoterics, including the names of twelve, forty-two, and seventy-two letters, and integrated them into this system.”
–Joseph Dan, Kabbalah: A Very Short Introduction, 2006, pp. 44.