"iter" is the Latin word for journey or path.

So, an iter-able is something that's "able to go on the journey, follow the path"

And an iter-ator is something that does what's needed to deal with the journey

Use "calculate" as a model:

Calculable is something that can be calculated

Calculator is something (or someone) that calculates

And a calculation is an event where something is being calculated.

So, that's how we get iteration, iterable, and iterator from the Latin "iter"