Pronto is tacked onto the end of an order to mean straight away. Get here pronto, do it pronto, pronto, please.
It is informal and slightly jokey, which softens an order while still giving one — saying pronto is friendlier than saying immediately and means the same thing. It came into English from Spanish, and it is the same Latin word as prompt.
1adverbprontoStraight away.
“Get down here pronto, or we'll miss the train!”
pronto is a time.
Spanish pronto comes from Latin promptus, ready. Prompt is the same word arriving by another road.
Latin
prōmptus
Spanish
pronto
English, today
pronto
Spanish pronto, from Latin prōmptus. a doublet of prompt.
Etymology from Wiktionary, CC BY-SA