the.com/refill

means To fill something again once it's been emptied, especially pouring more into a cup, container, or prescription.

from Straightforward carpentry of English — the prefix 're-' (again, back, Latin in origin, meaning repetition) bolted onto 'fill,' an old Germanic word for making something full. No trick to the word itself; the only sleight of hand happens at the soda fountain, not in the dictionary.