Green’s Dictionary of Slang

margarine or any other substitute (e.g. the short-lived butterine) for butter.

1878		Illus. Police News 6 July 4/5: Fined for Selling Bosh Butter [...] The magistrate’s clerk [...] said he believed there was a trade phrase of ‘bosch’ and another of butterine, applied to inferior articls sold by buttermen.
1909		J. Ware Passing Eng. of the Victorian Era 4/1: Bosh (Lower Official English). A term applied by market inspectors to butterine, oleomargarine and other preparations practically too long-windedly named to please the official mind. Now extended to all adulterants or adulterated food.