It is called so because its operation is the opposite of a rectifier used to make DC, which already existed when the word was introduced. A rectifier flipped around or inverted.

First you use diodes to turn the negative part of the AC wave positive.

So now you have a bunch of bumps that are all from 0 to 110V (in the case of 110VAC).

Next you use capacitors to store energy from the bump so the voltage doesn't drop anymore.

Then you add resistance to bring the voltage down to what you want to use.

That wave is more like the "pressure of the electricity" where more voltage means it goes further above/below zero, and the direction of that pressure(forward or backwards) is decided based on if it's above or below the zero line.

If it was a hose of water it's like turning on the tap and having water flow out of the hose, then get sucked back into the hose over and over.

For a brief moment there is no push or suction...that's your "0 point" otherwise it's either pushing the electrons down the wire. Or sucking them up the wire which means any individual electron might not actually "move" very much, much like the specific water molecules at the end of the hose would just go in and out of the tip rapidly...so too does the electrons

While DC power is a flat line at whatever voltage it is and that's more like a hose just shooting water out of it at a steady rate.

ELI5: You've got DC+ and DC- coming in, and AC1 and AC2 going out. Hook up + to AC1 and - to AC2, power goes forward, a crest. Now switch the cables quickly, - to AC1 and + to AC2. Now power is going backwards, a trough. Keep doing that 60 times a second and you've become a simple square wave inverter. Replace you with some circuitry and it's automatic. Normally you use more complicated components to generate a sinusoidal wave but the gist is the same, keep switching the DC input forwards and backwards and it creates the AC voltage wave