What is Burning Fluid?

Legal Definition
As used in policies of insurance, this term does not mean any fluid which will burn, but it means a recognized article of commerce, called by that name, and which is a different article from naphtha or kerosene. Putnam v. Insurance Co.. (C. Ct) 4 Fed. 764; Wheeler v. Insurance Co.., 6 Mo. App. 235; Mark v. Insurance Co., 24 Hun (N. Y.) 569.
-- Black's Law Dictionary