It's important to note that:
* Shawnee is a distinct Algonquian language, not simply a dialect of another language.
* Tecumseh likely also had some fluency in English due to his interactions with European settlers.
* He may have been familiar with other Algonquian languages spoken by his allies.
However, Shawnee was his native tongue and the language he would have used most often in his daily life and leadership.