Why is algebra called algebra?

Answer 1

Here's what the Online Etymology Dictionary says (etymology is the study of where words come from): "... from Arabic al jebr "reunion of broken parts," as in computation, used 9c(entury) by Baghdad mathematician Abu Ja'far Muhammad ibn Musa al-Khwarizmi as the title of his famous treatise on equations ("Kitab al-Jabr w'al-Muqabala" "Rules of Reintegration and Reduction"), which also introduced Arabic numerals to the West."

Before about the 9th century C.E. most of Western Europe used Roman numerals. The numerals we use now are a modified version of Arabic numbers and the early versions of our understanding of numbers probably developed from trade with people from the Arab world.

Or maybe not. I wasn't there.