Shia (n.)youdaoicibaDictYouDict[Shia 词源字典]
also Shiah, 1620s, a collective name for one of the two great Muslim sects, from Arabic shi'ah "partisans, followers, sect, company, faction" (from sha'a "to follow"). This is the proper use, but it commonly is used in English to mean "a Shiite." In Arabic, shi'ah is the name of the sect, shiya'iy is a member of the sect.

The branch of Islam that recognizes Ali, Muhammad's son-in-law, as the lawful successor of the Prophet; the minority who believed, after the death of the Prophet, that spiritual and political authority followed his family line, as opposed to the Sunni, who took Abu Bakr as the political leader of the community. The Arabic name is short for Shi'at Ali "the party of Ali."[Shia etymology, Shia origin, 英语词源]