noctambulist

noun

noct·​am·​bu·​list näk-ˈtam-byə-list 

: a person who walks while asleep : sleepwalker

Word History

Etymology

New Latin noctambulus "sleepwalker" (earlier noctambulō, with -ōn-, -ō, agent suffix, from Latin noct-, nox night entry 1 + -ambul-, noun derivative of ambulāre "to walk") + -ist entry 1 — more at amble entry 1

First Known Use

circa 1731, in the meaning defined above