Game concept
Nomadic Capital
The game also links it as Nomadic Capitals.
From the game's encyclopedia
Nomadic Capitals are moving sets of tents, livestock, people and horses. They can go from just a few sheep to a roaring horde.
Nomadic Rulers have a Nomadic Capital that they grow through Yurt Buildings and take with them when they Migrate. They cannot construct regular Buildings in Holdings.
The Nomadic Capital has a Faith and Culture representing the majority of the migrating people, which can be different from that of the Ruler.
Their whole Court travel with them, as well as their Family, Kurultai and Knights.
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.
Nomadic Capital is an entry of Crusader Kings III's in-game encyclopedia. The game explains it: "Nomadic Capitals are moving sets of tents, livestock, people and horses." It is part of Domicile. It covers Yurt Buildings. The game also links it as Nomadic Capitals. Patch 1.20.1.2, from game/common/game_concepts/mpo_game_concepts.txt and game/localization/english/game_concepts_l_english.yml.
Source: game/common/game_concepts/mpo_game_concepts.txt, game/localization/english/game_concepts_l_english.yml and the English localisation, Crusader Kings III 1.20.1.2.