Game concept
Borrowed Power
The game also links it as Borrowed Powers, Power, Powers, Borrowed Power's, Borrowed Powers', Power's, Powers'.
From the game's encyclopedia
A Diarch in an active Power Sharing has access to special Borrowed Powers.
These are special Character Interactions that mimic those their Liege have, or are other abuses of power. Examples include Revoking Titles from fellow Vassals, or siphoning away Gold from their Liege.
Many Borrowed Powers give the Liege an opportunity to Veto them.
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.
Borrowed Power is an entry of Crusader Kings III's in-game encyclopedia. The game explains it: "A Diarch in an active Power Sharing has access to special Borrowed Powers." It is part of Power Sharing. The game also links it as Borrowed Powers, Power, Powers, Borrowed Power's and 3 more. Patch 1.20.1.2, from game/common/game_concepts/04_ep2_game_concepts.txt and game/localization/english/game_concepts_l_english.yml.
Source: game/common/game_concepts/04_ep2_game_concepts.txt, game/localization/english/game_concepts_l_english.yml and the English localisation, Crusader Kings III 1.20.1.2.