Latin Potere -> French Pouvoir (same meaning than lat.) -> English Power.
Latin Potentialis -> French Potentiel -> English Potential
Latin impotens "lacking control, powerless, feeble; lacking self-control" (impotentem) -> French impotent -> English importent
Latin Potentia: power, might, force.
In all varieties of English "washing" and "cleaning" are close.
But "washing" means with water, and "cleaning" means removing the impurities.
You wash a dog, you don't clean it.
You can clean one of his ears, as it doesn't imply water, but impurities removal.
I don't know what would be the difference in Latin between washing and cleaning, I think to clean = purgare.