What is the X in X-mas?
c.1200, "piece of wood kindled at a fire," from fire (n.) + brand (n.). Figurative sense of "one who kindles mischief or passions" is from late 14c.
Isa. 7:4, Amos 4:11, Zech. 3:2, denotes the burnt end of a stick (Heb. 'ud); in Judg. 15:4, a lamp or torch, a flambeau (Heb. lappid); in Prov. 26:18 (comp. Eph. 6:16), burning darts or arrows (Heb. zikkim).