Game concept
Prisoner of War
The game also links it as Prisoners of War.
From the game's encyclopedia
A Prisoner of War is a Prisoner who's captured during a War, but not of importance to provide the captors with War Score.
Valuable Prisoners are released when the war ends, unlike prisoners of war, but can still be ransomed for release.
The game's text for patch 1.20.1.2. Words in blue are entries of the encyclopedia: hover one to read it, as in the game.
Prisoner of War is an entry of Crusader Kings III's in-game encyclopedia. The game explains it: "A Prisoner of War is a Prisoner who's captured during a War, but not of importance to provide the captors with War Score." The game also links it as Prisoners of War. Patch 1.20.1.2, from game/common/game_concepts/00_game_concepts.txt and game/localization/english/game_concepts_l_english.yml.
Source: game/common/game_concepts/00_game_concepts.txt, game/localization/english/game_concepts_l_english.yml and the English localisation, Crusader Kings III 1.20.1.2.