Hashem’s name YUD KAY VAV KAY is abbreviated in certain sidurim to YUD YUD. Why? It should be abbreviated to YUD KAY as there is only one YUD in YUD KAY VAV KAY. They say in the Kabbalah there is a 3rd YUD travelling around in 3 dimensions – please explain
The abbreviation Yud Yud derives from the first Yud of the Name Yud Kay Vav Kay, and the last Yud of the Name Ado-nai. The reason for this abbreviation is one of the basic intentions in uttering Hashem’s Name is that the Name YKVK is revealed by means of the name Ado-nai — which is why we read YKVK, but articulate Ado-nai.
It goes without saying that there is much kabbalistic meaning in this matter, which is beyond the current discussion. This also applies to the concept of the three letter yud’s, which is a discussion unto itself.