Where does “??” come from?

?? (Middle Persian) comes from Old Persian ??, from Proto-Iranian máH, from Proto-Indo-Iranian maH, from Proto-Indo-European meh₁ — prohibitive particle.

Ancestry of “??”, step by step

StepLanguageWordMeaning
1Old Persian??—
2Proto-IranianmáH—
3Proto-Indo-IranianmaHdo not; prohibitive particle
4Proto-Indo-Europeanmeh₁prohibitive particle
Every word from Proto-Indo-European meh₁ →Every word from Proto-Indo-Iranian maH →Every word from Proto-Iranian máH →