Game concept
Weak Hook
The game also links it as Weak Hooks.
From the game's encyclopedia
A Weak Hook is a fairly common Hook that you might have on a character who owes you a favor, or that you have manipulated to do your will.
While there are many interactions where a Weak Hook can be used, for example in Marriage proposals, they cannot be used to force someone to become your Agent in a Murder and do not provide a passive benefit (for that, a Strong Hook is necessary.)
Every child born to a Noble House also owes the House Head an initial Weak Hook.
Once a Weak Hook is used, it is spent.
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.
Weak Hook is an entry of Crusader Kings III's in-game encyclopedia. The game explains it: "A Weak Hook is a fairly common Hook that you might have on a character who owes you a favor, or that you have manipulated to do your will." It is part of Hook. The game also links it as Weak Hooks. 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.