The original name of Bangalore was Benda Kaal Ooru. This rather unsavoury name came about when a king named Vira Ballala lost his way on a hunting expedition and was eventually offered boiled beans by an old lady. In recognition of this act of kindness, he named the place Benda Kaal Ooru.
Along came the British and, since they really couldn't be arsed to say Benda Kaal Ooru, they simplified the name to Bangalore. Nor can the locals apparently be arsed to say Benda Kaal Ooru, since the new moniker is the "phonetic variation" of the hard-to-pronounce original.
The new name was announced by chief minister of Karnataka state, Dharam Singh, in response to a demand from a group of Kannada-language writers. One of them, UR Ananthamurthy, reckons the locals already call the place Bengaluru, so no big deal.