Bittereinders were a faction of Boer

Boer

Boer is the Dutch and Afrikaans word for farmer, which came to denote the descendants of the Dutch-speaking settlers of the eastern Cape frontier in Southern Africa during the 18th century, as well as those who left the Cape Colony during the 19th century to settle in the Orange Free State,...

 guerrilla fighters, resisting the forces of the British Empire

British Empire

The British Empire comprised the dominions, colonies, protectorates, mandates and other territories ruled or administered by the United Kingdom. It originated with the overseas colonies and trading posts established by England in the late 16th and early 17th centuries. At its height, it was the...

 in the later stages of the Second Boer War

Second Boer War

The Second Boer War was fought from 11 October 1899 until 31 May 1902 between the British Empire and the Afrikaans-speaking Dutch settlers of two independent Boer republics, the South African Republic and the Orange Free State...

 (1899-1902).

By September 1900, the conventional forces of the South African Republic

South African Republic

The South African Republic , often informally known as the Transvaal Republic, was an independent Boer-ruled country in Southern Africa during the second half of the 19th century. Not to be confused with the present-day Republic of South Africa, it occupied the area later known as the South African...

 and the Orange Free State

Orange Free State

The Orange Free State was an independent Boer republic in southern Africa during the second half of the 19th century, and later a British colony and a province of the Union of South Africa. It is the historical precursor to the present-day Free State province...

 had been largely defeated by the British army. The remnants of Boer government resolved to fight on in a guerrilla war, to try to force the British to retreat from the territory. As it became clear that military victory was unlikely, opinion among the guerrillas divided between those who wanted to secure a negotiated peace and those who preferred to fight on to 'the bitter end'. The decision to fight was given particular currency by British use of concentration camps to pacify the Boer population.

The word is derived from the Dutch language

Dutch language

Dutch is a West Germanic language and the native language of the majority of the population of the Netherlands, Belgium, and Suriname, the three member states of the Dutch Language Union. Most speakers live in the European Union, where it is a first language for about 23 million and a second...

 upon which the Afrikaans

Afrikaans

Afrikaans is a West Germanic language, spoken natively in South Africa and Namibia. It is a daughter language of Dutch, originating in its 17th century dialects, collectively referred to as Cape Dutch .Afrikaans is a daughter language of Dutch; see , , , , , .Afrikaans was historically called Cape...

 language of the Boers (later known as Afrikaners) is based. The words bitter einder (singular, the final "s" denotes plural) literally mean "bitter-ender" denoting someone who is "willing to fight to the bitter end".

Taken more generally, it could be used as another name for a "war party" (a faction within a political or military group favoring the waging of war) or for any group which does not wish to diminish its "fighting spirit" wanting to fight it out to the "bitter end."