What is the X in X-mas?
c.1600, from Irish lupracan, metathesis from Old Irish luchorpan literally "a very small body," from lu "little" (from PIE *legwh- "having little weight;" see light (adj.)) + corpan, diminutive of corp "body," from Latin corpus "body" (see corporeal). Commonly spelled lubrican in 17c. English. Leithbragan is Irish folk etymology, from leith "half" + brog "brogue," because the spirit was "supposed to be always employed in making or mending a single shoe."