Llenar comes from the Latin plere (“to fill”), as we’ve previously discussed. But here’s another English word that comes from the same Latin root: expletive, yes, that euphemism for vulgar words!
Expletive literally means to “fill” with the expansive ex– prefix which, taken together, means, “to fill out your words.” An expletive is literally filling a conversation with words when you don’t know what else to say!