ambulation (n.)

"to move easily and gently without hard shocks," as a horse does when it first lifts the two legs on one side and then the two on the other, early 14c., from Old French ambler, of a horse or other quadruped, "go at a steady, easy pace" (12c.), from Latin ambulare "to walk, to go about, take a walk," perhaps a compound of ambi- "around" (from PIE root *ambhi- "around") and -ulare, from PIE root *el- "to go" (source also of Greek ale "wandering," alaomai "wander about;" Latvian aluot "go around or astray"). Until 1590s used only of horses or persons on horseback. Related: Ambled; ambling.

"sleep-walking," 1721; see noct- "night" + ambulation "act of walking about." Related: Noctambulist; noctambulism; noctambulant.