www.alphadictionary.com

From:
Gilbert and Sullivan, the two Victorian
gentlemen famous for their enduringly popular light operas.


Pooh-Bah is a dignitary (supposedly Japanese) in the Mikado, one of
their best-known works. I can't find him actually called grand in the
original but he is described as Lord High Everything Else. Along with
the Lord High Executioner and the Mikado himself he provides a
caricature of grandiose pomposity for Gilbert and Sullivan to poke fun
at. You will find huge amounts of information - plot summary,
libretto, audio files, reviews and more - at:
http://math.boisestate.edu/gas/mikado/html/mikado.html .

I can't actually prove that Gilbert (who was in charge of words while
Sullivan composed the music) invented the name himself but I have
always believed this to be the case. Maybe this confirms your feeling
that there was a literary/musical comedy background (with a political
flavour?) to the name. Also, it fits with all the other made-up names
in the Mikado: Yum-Yum, Ko-Ko and Nanky-Poo for starters.

Another page at the same site:
http://math.boisestate.edu/gas/index.html#gilbert
will refer you to lots of information about Gilbert if you want to try
to establish that this was definitely the first-ever use of the name.

Let me know if this needs any follow-up.

Leli