Game concept
Risk of Injury
The game also links it as Injure, Injury Risk.
From the game's encyclopedia
Characters in Single Combats run the risk of hurting themselves, either by accidentally opening their guard to their opponent, or simply injuring themselves with their own weapon. As they fight, they also build Risk of Injury.
Duels that go on longer make it easier to hurt yourself.
The counterpart to Risk of Injury is Likelihood of Success.
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.
Risk of Injury is an entry of Crusader Kings III's in-game encyclopedia. The game explains it: "Characters in Single Combats run the risk of hurting themselves, either by accidentally opening their guard to their opponent, or simply injuring themselves with their own weapon." It is part of Single Combat. The game also links it as Injure and Injury Risk. 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.