What is the X in X-mas?
word used by a vassal to address his superior or lord in the feudal system, c.1300, from Anglo-French lige (late 13c.), Old French lige "(feudal) liege, free, giving or receiving fidelity," perhaps from Late Latin laeticus "cultivated by serfs," from laetus "serf," which probably is from Proto-Germanic *lethiga- "freed" (cf. Old English læt "half-freedman, serf;" Old High German laz, Old Frisian lethar "freedman"), from PIE root *le- "let go, slacken" (see let (v.)). Or the Middle English word may be directly from Old High German leidig "free." As a noun from late 14c., both as "vassal" and "lord." Hence, liege-man "a vassal sworn to the service and support of a lord, who in turn is obliged to protect him" (mid-14c.).