One of the earliest known legends about leprechauns (which means little bodies in Irish) is the story about the King Of Ulster. Once upon a time there was a king in Ireland name Mac Leda, who was the King Of Ulster, in northern Ireland. As he slept, it is said that little leprechauns tried to drag Mac Leda into the sea, but the cold water woke him and he was able to catch them. The leprechauns granted Mac Leda three wishes, for their freedom, with his first wish being that he would be able to breathe under water, the next time! Other Irish folklore maintain that leprechauns were often shoemakers, who if you were lucky enough to catch one, he would grant wishes or give you his gold. But Leprechauns are well known to play a trick or two and get off scott free, pardon the pun, as evidenced by this limerick.
Nine and ninety treasure crocks,
this keen miser fairy hath, hid in mountains, woods, and rocks,
ruin and round tower, cave and rath and where the cormorants build (cormorants are birds)
From times of old, guarded by him, each of them filled full to the brim with gold!
I caught him at work one day, myself, in castle ditch, where foxglove grows,
a wrinkled, wizened and bearded elf, spectacles stuck on his pointed nose,
silver buckles to his hose, leather apron shot in his lap...
...A grasshopper on my cap!
Away the moth flew! Buskins (boots) for a fairy prince. Brogues (shoes) for his son, pay me well, pay me well, when the job is done!
The rogue was mine beyond a doubt I stared at him he stared at me servant!
Sir! an Hmph! says he and pulled a snuff box out he took a long pinch looked better pleased then the little Lepracaun offered the box with a whimsical grace Poof! he flung the dust in my face!
and while I sneezed...was gone!
The Leprechaun, by William Allingham