dement

[dih-ment] /dɪˈmɛnt/
verb (used with object), Obsolete
1.
to make mad or insane.
Origin
1535-45; < Late Latin dēmentāre to deprive of mind, equivalent to Latin dēment- (stem of dēmēns) out of one's mind (dē- de- + ment- (stem of mēns) mind) + -āre infinitive suffix
British Dictionary definitions for dement

dement

/dɪˈmɛnt/
verb
1.
(intransitive) to deteriorate mentally, esp because of old age
2.
(transitive) (rare) to drive mad; make insane
Word Origin
C16: from Late Latin dēmentāre to drive mad, from Latin de- + mēns mind
Word Origin and History for dement
v.

1540s, "to drive mad," probably from Middle French démenter, from Late Latin dementare "to drive out of one's mind," from phrase de mente (a less technical term than insanitas), from de + mente, ablative of mens mind" (see mind (n.)).