The word "algebra" originally comes from the word "al-jabr" in Arabic, which means restoration or reunification. "Al-jabr" was used to refer to the process of simplifying equations that is used in algebra.
The first known use of "al-jabr" to refer to mathematical reduction was by Abu Ja'far Muhammad ibn Musa al-Khwarizmi in the title of a treatise on mathematics in the 9th century. The word was borrowed by Medieval Latin and later by Middle English, at which time its spelling became "algebra." The mathematical term "algorithm" comes from the same Arabic roots. Algebra continues to describe the process of mathematical reduction in many languages.