For the last five years, a team of researchers from Cambridge University and Queen’s University Belfast have meticulously combed through manuscripts dating all the way back to the 6th century in order to revise an online dictionary of medieval Irish. In addition to discovering about 500 previously lost words, they also unearthed new etymological information about a word you definitely already know: leprechaun.

According to BBC News, the scholars believe leprechaun, from the Irish leipreachán, isn’t an Irish original. Based on their research, it’s derived from Luperci, the Latin word for a group of priests who celebrated an ancient Roman festival called Lupercalia, which took place on February 15. Though we don’t exactly know the origin of Lupercalia, it’s thought to have included a purification ritual that involved swimming. After an animal sacrifice (and a few other weird activities), two possibly naked boys would run through the city streets whipping women with thongs made from the skin of the sacrificial animal, which was said to increase fertility.

The first known leprechaun appearance in Irish literature was in a folktale from the Middle Ages in which Fergus mac Léti, the King of Ulster, awakens from a seaside nap to leprechauns trying to drag him into their underwater abode—suggesting that leprechauns are water-dwellers. Maybe the Irish storytellers who originated that fable broadly interpreted the purification theme from Lupercalia to be more literally related to water. Or, maybe the element of Lupercalia they co-opted for their Irish mascot was the idea of small people (specifically male) causing mischief in the streets, which pretty calls to mind our current conception of leprechauns as tiny tricksters.

Either way, the revelation about leprechauns’ Latin roots is a nod to the project’s success in enriching our knowledge of the Irish language, from which English has borrowed more than you might realize. And, as Greg Toner of Queen’s University Belfast told BBC News, about one third of the online dictionary’s 20,000 monthly visitors are from the U.S.

“A key aim of our work has been to open the dictionary up, not only to students of the language but to researchers working in other areas such as history and archaeology, as well as to those with a general interest in medieval life,” he told BBC News.

You can explore the dictionary here.

[h/t BBC News]