Costa Rican Spanish Word of the Day: ¡Aca!

¡Aca! is an interjection that Costa Rican farmers will use to yell at their cows. They simply scream it over an over again when trying to herd their cattle.

Perhaps it isn't actually an interjection, which is a word that is "interjected" in a sentence without a market grammatical connection with the other parts within. Perhaps ¡Aca! actually does originate from an actual command, making it a verb--or maybe even shorthand for a longer sentence. I will try to get to the bottom of this etymological issue when I go to Costa Rica in January.