The story
From concentration + camp. In later use partly after German Konzentrationslager, itself a calque of the English term.
First known use, by meaning
- from 19th c. A camp where large numbers of people, especially political prisoners, prisoners of war, refugees etc., are detained for the purpose of confining them in one place, typically with inadequate or inhumane facilities.
- from 20th c. A situation of overcrowding and extremely harsh conditions.
Etymology from Wiktionary, CC BY-SA 4.0.