dementia n.

"drive mad, bring to a state of dementia," now obsolete or archaic but for the past-participle adjective demented, 1540s, probably from French démenter, from Late Latin dementare "to drive out of one's mind," from stem of Latin demens "out of one's senses, insane, raving, foolish; distracting, wild, reckless" (a less technical term than insanitas), from phrase de mente, from de "from, away from" (see de)+ mente, ablative of mens "mind" (from PIE root *men- (1) "to think").

word-forming element in names of countries, diseases, and flowers, from Latin and Greek -ia, noun ending, in Greek especially used in forming abstract nouns (typically of feminine gender); see -a (1). The classical suffix in its usual evolution (via French -ie) comes to Modern English as -y (as in familia/family, also -logy, -graphy). Compare -cy.

In paraphernalia, Mammalia, regalia, etc. it represents Latin or Greek -a (see -a (2)), plural suffix of nouns in -ium (Latin) or -ion (Greek), with formative or euphonic -i-.

1640s, "developed or ripe before the usual time," originally of plants, with -ous + Latin praecox (genitive praecocis) "maturing early," from prae "before" (see pre-) + coquere "to ripen," literally "to cook" (from PIE root *pekw- "to cook, ripen").

Originally of flowers or fruits. Figurative use, of persons, dates, etc., "characteristic of early maturity," by 1670s. Related: Precociously; precociousness. Obsolete princock "pert, forward, saucy boy or youth" (16c.-18c.) might be a rude, low slang folk-etymology alteration of Latin praecox.