1. dwarf or sprite.
2. conventionalized literary representation of this figure as a little old man who will reveal the location of a hidden crock of gold to anyone who catches him.

Word History: Nothing seems more Irish than the leprechaun; yet hiding within the word leprechaun is a word from another language entirely. If we look back beyond Modern Irish Gaelic luprachán and Middle Irish luchrupán to Old Irish luchorpán, we can see the connection. Luchorpán is a compound of Old Irish lú, meaning “small,” and the Old Irish word corp, “body.” Corp is borrowed from Latin corpus (which we know from habeas corpus). Here is a piece of evidence attesting to the deep influence of Church Latin on the Irish language. Although the word is old in Irish it is fairly new in English, being first recorded in 1604.

Hmmm. Something I've found out while searching for words at www.dictionary.com. That is a very good website, with dictionary, theasurus, encylopedia etc.