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"ARABIC LIGATURE UIGHUR KIRGHIZ YEH WITH HAMZA ABOVE WITH ALEF MAKSURA ISOLATED FORM" (U+FBF9).
The shortest-named character is
🐂
"OX" (U+1F402)
O_o
Bo?
Ra?
Pi?
Oz? (you didn't say PERSON name :P )
Li?
(most of that list is somewhat arguable but I have KNOWN people whose name was 'Bo', not it's-short-for-something "Bo" but 'Bo')
the REALLY sad part is that my conscious mind leaped into the fray to respond to the perceived statement ("of human names, only one has two letters") and all it could come up with was "Bo"
that's pathetic, there's gotta be plenty of others that I can't think of
(but in fairness I'm on my first batch of caffeine for the day and JUST took my pills an hour ago (my sleep schedule's been all over the place, don't even ask))
exactly
and I'm a WRITER
this shouldn't have been hard for me (I have a character in a work-in-progress CALLED Jo, FFS)