From wiki:
The term gasoline originated from the trademark terms Cazeline and Gazeline, which were stylized spellings and pronunciations of Cassell, the surname of British businessman John Cassell...
In the course of business, he learned that the Dublin shopkeeper Samuel Boyd was selling a counterfeit version of the fuel cazeline, and, in writing, Cassell asked Boyd to cease and desist selling fuel using his trademark. Boyd did not reply, and Cassell changed the spelling of the trademark name of his fuel cazelline by changing the initial letter C to the letter G, thus coining the word gazeline. By 1863, North American English usage had re-spelled the word gazeline into the word gasolene; by 1864, the gasoline spelling was the common usage.
Not from wiki:
Petrol isn't a great name either, given that it's not petroleum but a petroleum products (and one of many).