When we wrap, there seems to be a prevalent custom to incorporate the shapes Dalet, Yod and Shin in the strap on the hand/arm (depending on one's custom (discussed in Sefer Ta'amei Haminhagim page 13 and diagrams pp. 621-626) (Minhagei Yeshurun P. 212). While I know that there are kabbalistic sources and other explanations for the seven wrappings around the arm, and that many of the laws are reputed to be unexplained as examples of halacha lemoshe misinai, I am wondering where the idea of spelling out God's name with the 3 letters comes from (and I don't have access to the Otzar Minhagei Yeshurun and the Ktzot hashulchan).

A quick look at printed alphabets of ancient Hebrew show that the shape of the letters is not the same as we have now so wrapping straps to mimic current shapes would indicate that the minhagim are relatively recent. Where does this idea/practice originate?

When we wrap, there seems to be a prevalent custom to incorporate the shapes Dalet, Yod and Shin in the strap on the hand/arm (depending on one's custom (discussed in Sefer Ta'amei Haminhagim page 13 and diagrams pp. 621-626) (Minhagei Yeshurun P. 212). While I know that there are kabbalistic sources and other explanations for the seven wrappings around the arm, and that many of the laws are reputed to be unexplained as examples of halacha lemoshe misinai, I am wondering where the idea of spelling out God's name with the 3 letters comes from (and I don't have access to the Otzar Minhagei Yeshurun and the Ktzot hashulchan).

A quick look at printed alphabets of ancient Hebrew show that the shape of the letters is not the same as we have now so wrapping straps to mimic current shapes would indicate that the minhagim are relatively recent. Where does this idea/practice originate?