dement
/dɪˈmɛnt
/noun archaic
A person suffering from dementia.Nowadays, no sooner is an asylum built than it is filled with maniacs, suicidal melancholics, or senile dements in need of care and treatment....
- The Picts, to most people outside Scotland, are a totally mysterious and marginal dement in the ancient population of northern Britain.
Origin
Late 15th century (as an adjective in the sense 'demented'): from French dément or Latin demens, dement- 'insane'. The noun use dates from the late 19th century.