Game concept
Escalated Peasant Faction
The game also links it as Escalated Peasant Factions.
From the game's encyclopedia
The Escalated Peasant Faction is populated by Counties with low Popular Opinion that already enforced demands of a Peasant Faction on one of your Vassals. Lead by an infamous leader, the faction is dangerous and capable of breaking away from your Realm.
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.
Escalated Peasant Faction is an entry of Crusader Kings III's in-game encyclopedia. The game explains it: "The Escalated Peasant Faction is populated by Counties with low Popular Opinion that already enforced demands of a Peasant Faction on one of your Vassals." It is part of Faction. The game also links it as Escalated Peasant Factions. 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.