This is what's in Wikipedia -
"In Irish mythology, a leprechaun (Irish: leipreachán) is a type of male faerie said to inhabit the island of Ireland. They are a class of "faerie folk" associated in Irish folklore with the Tuatha Dé Danann and other quasi-historical peoples said to have inhabited Ireland before the arrival of the Celts.
Leprechauns usually take the form of old men who enjoy partaking in mischief. Popular depiction shows them as being no taller than a small child. Their trade is that of a cobbler or shoemaker. They are said to be very rich, having much buried treasure. According to legend, if anyone keeps an eye fixed upon one, he cannot escape, but the moment the gaze is withdrawn, he vanishes."
I love mythology. The human mind is capable of such fabulously imaginative creativity, isn't it?