leprechaun

The word comes from Irish leipreachán, luprachán, via Middle Irish luchrupán, from Old Irish luchorpán. It's traditionally explained as lú ("small") + corp ("body," from Latin corpus), though some scholars instead trace it to Latin Lupercī, the priests of Lupercus, who may have been misread by medieval Irish scribes as a race of tiny ancient beings.

If the Lupercī theory holds, a name for Roman priests was misunderstood centuries later in Irish scholarship and reshaped into the label for a small mythical figure, its suffix possibly assimilated to the Irish diminutive -achán.

It shares its diminutive suffix pattern with clurichaun, another small Irish sprite, and possibly its root with Latin corpus, ancestor of English 'corpse' and 'corporal.'