Yamato is the name of a Japanese dynasty (approximately 250–710 AD), that was located in Ancient Japan with the capital city at Fujiwara. The Yamato are the ancestors of modern Japanese people and were the first people to unify and conquer all of Japan. In Age of Empires, they are one of the three playable East Asian civilizations and make an excellent offensive civilization on sea maps. They also have a self-sufficient economy giving them a slight edge in the beginning of the game. The equivalent civilization is known as Japanese in both Age of Empires II and Age of Empires III.
Historical or legendary figures (except Himiko), represented by Yamato AI players, belong to the Imperial House of Japan, who hailed from Kyushu, according to Kojiki & Nihon Shoki. Meanwhile, Queen Himiko likely belonged to another dynasty who ruled Yamatai, which then did not exert its authority over all early Honshu Japanese polities; as Sanguozhi mentioned Himiko's conflict against king Himikoko of Kuna.
A more encompassing civilizational name would have been Wa, the native Japanese first singular person pronoun "I, me", best represented by 我, which is read, meaning-based, as wa (わ/ワ).