What is the X in X-mas?
"fastened," mid-14c., in figurative sense of "compelled," from bounden, past participle of bind (v.). Meaning "under obligation" is from late 15c.; the literal sense "made fast by tying" is the latest recorded (1550s).
"ready to go," c.1200, boun, from Old Norse buinn past participle of bua "to prepare," also "to dwell, to live," from Proto-Germanic *bowan (cf. Old High German buan "to dwell," Old Danish both "dwelling, stall"), from PIE root *bheue- "to be, exist, dwell" (see be). Final -d is presumably through association with bound (adj.1).
"limit," c.1200, from Anglo-Latin bunda, from Old French bonde "limit, boundary, boundary stone" (12c., Modern French borne), variant of bodne, from Medieval Latin bodina, perhaps from Gaulish. Now chiefly in out of bounds, which originally referred to limits imposed on students at schools.
"to form the boundary of," also "to set the boundaries of," late 14c., from bound (n.). Related: Bounded; bounding.
"to leap," 1580s, from French bondir "to rebound, resound, echo," from Old French bondir "to leap, rebound; make a noise, beat (a drum)," 13c., ultimately "to echo back," from Vulgar Latin *bombitire "to buzz, hum" (see bomb (n.)), perhaps on model of Old French tentir, from Vulgar Latin *tinnitire.