On a related note, 'pooci', in tamil means worm, or insect. That could be
the origin of booci in telugu. I personally haven't heard booci refer to a
ghost - in my childhood, I heard it being used to refer to particularly
unpleasant insects like caterpillars.
There were a lot of legends about the French general 'Bussi', who sided
with Vijayaraama Raaju to fight against the bobbili kingdom: I have heard
of the legends too, of mothers using this guy's name to silence their
unruly offspring, but I feel the origin of booci in Telugu is definitely
older than bobbili yudhdham.
Just my 2 pennies.
Regards
Nasy