Why is the ninth month called September?
1590s, from Latin delirium "madness," from deliriare "be crazy, rave," literally "go off the furrow," a plowing metaphor, from phrase de lire, from de "off, away" (see de-) + lira "furrow, earth thrown up between two furrows," from PIE *leis- "track, furrow."
delirium de·lir·i·um (dĭ-lēr'ē-əm)
n. de·lir·i·ums or de·lir·i·a (-ē-ə)
A temporary state of mental confusion resulting from high fever, intoxication, shock, or other causes, and characterized by anxiety, disorientation, memory impairment, hallucinations, trembling, and incoherent speech.