From the 1911 Encyclopedia, courtesy of About.com.
Various derivations of the word "algebra," which is of Arabian origin, have been given by different writers. The first mention of the word is to be found in the title of a work by Mahommed ben Musa al-Khwarizmi (Hovarezmi), who flourished about the beginning of the 9th century. The full title is "ilm al-jebr wa'l-muqabala", which contains the ideas of restitution and comparison, or opposition and comparison, or resolution and equation, "jebr" being derived from the verb "jabara", to reunite, and "muqabala", from "gabala", to make equal. (The root "jabara" is also met with in the word "algebrista", which means a "bone-setter," and is still in common use in Spain.)