Why terminals of opamp are called as inverting and noninverting?

In an op-amp, an input on the inverting terminal drives the output in the opposite direction, while an input on the non inverting terminal drives the output in the same direction.

In a normal closed loop negative feedback configuration, there is feedback from output to inverting input, so that the output becomes a known function of input. So long as you stay within limits, the output will go to whatever value is required to make the inputs be the same.