I’ve written this modern midrash to explain it.
One day R. Nachman got a phonecall from his mother, who was in a chatty mood. While she spoke R. Nachman doodled on a scrap of paper. He wrote:
na, nach, nachma, nachman
starting with the first letter of his name and adding one more letter each time till the name was complete. Then – noticing that his town of birth matched the progression – he added:
M’Uman (from Uman)
He thought it looked rather neat, and used the scrap as a bookmark in his siddur.
After his death, the scrap was discovered by one of his students. However, instead of discarding it, or preserving it as a private keepsake, the student publicised it as a good-luck charm.
Because it was so obviously devoid of any meaning, it was an instant success with people of whom the same was true, and before long pseudo-religious Jewish hooligans were graffiti-spraying it onto public property all over the world.
Tonight, 23 Tammuz 5775, is the 93rd anniversary of the discovery of the “Petek” [note], called by some “Chag Hapetek” (The festival of the note). It has even been said in all seriousness: “Basically the whole universe stands on the holy Petek”.
Although I am far from being a rationalist, I find it worrying that this kind of lunacy – quite apart from the associated vandalism – is coming to be associated with mainstream Jewish observance.