Why is the word Texian used instead of Texan?

Answer 1

Actually, most people in the US, use the word Texan to denote someone who comes from the state of Texas.

Texians was originally used as a name for immigrants from the United States and countries other than Mexico who became residents in the Tejas and Coahuila areas of Mexico, of which, much would later be called Texas. The term Texian was the preferred term for the people who came from the Republic of Texas, before Texas became a state.

Texian, is the preferred term, used today by those from Texas.

Answer 2

The term "Texian" was used before Texas gained statehood to distinguish the residents from the Mexican state of Coahuila y Tejas. It was a way for the settlers to establish a separate identity during their fight for independence. After Texas became a state, the term "Texan" became more commonly used.