"The whole numbers were made by God, all else is the work of mankind."
-German mathematician Leopold Kronecker
A Little History...

Math evolved greatly out of the Dark Ages and many concepts had to be extended and generalized.
Apart from the integers, rational and irrational numbers were introduced which completed the
real number system. However, this was only enough until the question of finding solutions to x²=-1 was brought up.
These type of questions are what lead to the creation of complex numbers.

It was Gauss who introduced the term Complex Number in 1831 after the idea had been
passed on by various mathmaticians who originally had the idea of imaginary numbers from a cubic
equation. It was Descartes who coined the term imaginary in about 1637.
He said,

"“For any equation one can imagine as many roots [as its degree would suggest],
but in many cases no quantity exists which corresponds to what one imagines.”


To learn more about the history of the complex number system, visit:
A Short history of Complex Numbers
History of Complex Numbers