"sleep-walking," 1721; see noct- "night" + ambulation "act of walking about." Related: Noctambulist; noctambulism; noctambulant.
also nocti-, word-forming element meaning "night, by night, at night," from Latin nox (genitive noctis) "night," from PIE *nekwt- "night" (see night).
"act of walking about," 1570s, from Latin ambulationem (nominative ambulatio), noun of action from past-participle stem of ambulare "to walk, go about" (see amble (v.)). The word was used earlier in reference to the spread of disease (1540s).