1794 (as somnambulation), from Mod.L. somnambulus "sleepwalker," from L. somnus "sleep" (see somnolence) + ambulare "to walk" (see amble). Won out over noctambulation. To talk in one's sleep is somniloquence (1841).
Main Entry: som·nam·bu·lism Pronunciation: säm-'nam-by&-"liz-&m Function: noun 1: an abnormal condition of sleepin which motor acts (as walking) are performed 2: actions characteristic of somnambulism —som·nam·bu·lis·tic/(")säm-"nam-by&-'lis-tik/adjective
Main Entry: som·nam·bu·list Pronunciation: -l&st Function: noun :SLEEPWALKER