What was the original job of leprechauns?

According to many Irish legends, the Leprechauns are small men, perhaps male fairies, that are dressed as a shoemaker would be, though their outfits are a very rich green. It is said that when they are hidden, they can often be detected by the sound of a shoemaker's hammer tapping against the soles of a shoe, as they work upon it. Many people would think that they would be searching for gold and collecting it, and in a way you would be correct, but this is not their main job, nor their main goal in life. Due to their attire and the way they can be found, many Irish folklore stories will say that they mend shoes.