Refusing to "bite the cartridge" was a turn of phrase used by the British in India of Native Indian soldiers (sepoy

Sepoy

A sepoy was formerly the designation given to an Indian soldier in the service of a European power. In the modern Indian Army, Pakistan Army and Bangladesh Army it remains in use for the rank of private soldier.-Etymology and Historical usage:...

s) who had mutinied in 1857.

It derives from the act of biting open a paper cartridge

Paper cartridge

Paper cartridge refers to one of various types of small arms ammunition used before the advent of the metallic cartridge. These cartridges consisted of a paper cylinder or cone containing the bullet, gunpowder, and, in some cases, a primer or a lubricating and anti-fouling agent...

 containing gunpowder

Gunpowder

Gunpowder, also known since in the late 19th century as black powder, was the first chemical explosive and the only one known until the mid 1800s. It is a mixture of sulfur, charcoal, and potassium nitrate - with the sulfur and charcoal acting as fuels, while the saltpeter works as an oxidizer...

 in order to load contemporary rifles.

One of the alleged causes of the Indian Rebellion of 1857

Indian Rebellion of 1857

The Indian Rebellion of 1857 began as a mutiny of sepoys of the British East India Company's army on 10 May 1857, in the town of Meerut, and soon escalated into other mutinies and civilian rebellions largely in the upper Gangetic plain and central India, with the major hostilities confined to...

 were rumours that the grease on these cartridges designed to keep them dry was, variously, pork or beef fat (pork being abhorrent to Muslim

Muslim

A Muslim, also spelled Moslem, is an adherent of Islam, a monotheistic, Abrahamic religion based on the Quran, which Muslims consider the verbatim word of God as revealed to prophet Muhammad. "Muslim" is the Arabic term for "submitter" .Muslims believe that God is one and incomparable...

s, cows being sacred to Hindu

Hindu

Hindu refers to an identity associated with the philosophical, religious and cultural systems that are indigenous to the Indian subcontinent. As used in the Constitution of India, the word "Hindu" is also attributed to all persons professing any Indian religion...

s), thus their refusal to bite them.