Noonday Demon

The term Noonday Demon (also Noonday Devil, Demon of Noontide, Midday Demon or Meridian Demon) is used as a personification and synonym for acedia. It indicates a demonic figure thought to be active at the noon hour which inclines its victims (usually monastics) to restlessness, excitability and inattention to one's duties.
It comes from biblical sources: Psalm 90:6 of the Hebrew Bible reads "mi-ketev yashud tsohorayim": from destruction that despoils at midday. This phrase was translated into Alexandrian Greek in the Septuagint into. "apo pragmatos diaporeuomenou en skotei apo symptwmatos kai daimoniou mesembrinou" ([you need not fear] the pestilence that walks in darkness, nor the destruction that wastes at noonday.). In the Vulgate, Jerome's translation of the Septuagint into Latin, we can find a personification in the daemonium meridianum ("Non timebis . . . ab incursu et daemonio meridiano"). This demonic personification is kept in the Catholic Douay-Rheims translation of the Old Testament of 1609 (Psalms 90:6). An exception is King James Version of 1611, where the translation follows the original Hebrew: “the destruction that wasteth at noonday”.
In the writings of Evagrius Ponticus, a Christian monk and ascetic, the Noonday Demon is specifically responsible for acedia, which he describes as "daemon qui etiam meridianus vocatur", attacking the cenobites most frequently between the hours of ten and two. It caused a sentiment characterized by exhaustion, listlessness, sadness, or dejection, restlessness, aversion to the cell and ascetic life, and yearning for family and former life.