How do you say leprechaun in Gaelic?

There isn't one single word for "leprechaun" in Gaelic. The word "leprechaun" is an anglicization of the Irish *luchorpán*. However, even *luchorpán* isn't a direct translation of a concept; it's a word used to describe a specific type of fairy. There's no single word equivalent across all dialects of Irish Gaelic.