demonyoudaoicibaDictYouDict[demon 词源字典]
demon: [14] English acquired this word from Latin in two forms, classical Latin daemōn and medieval Latin dēmōn, which were once used fairly interchangeably for ‘evil spirit’ but have now split apart. Demon retains the sense ‘evil spirit’, but this was in fact a relatively late semantic development. Greek daímōn (source of Latin daemōn) meant ‘divine power, fate, god’ (it is probably related to Greek daíomai ‘distribute, allot’, which comes from an Indo- European base whose descendants include English tide and time).

It was used in Greek myths as a term for a minor deity, and it was also applied to a ‘guiding spirit’ (senses now usually denoted by daemon in English). It seems to be from this latter usage that the sense ‘evil spirit’ (found in the Greek Septuagint and New Testament and in the Latin Vulgate) arose.
=> pandemonium, time, tide[demon etymology, demon origin, 英语词源]
demon (n.)youdaoicibaDictYouDict
c. 1200, from Latin daemon "spirit," from Greek daimon "deity, divine power; lesser god; guiding spirit, tutelary deity" (sometimes including souls of the dead); "one's genius, lot, or fortune;" from PIE *dai-mon- "divider, provider" (of fortunes or destinies), from root *da- "to divide" (see tide (n.)).

Used (with daimonion) in Christian Greek translations and Vulgate for "god of the heathen" and "unclean spirit." Jewish authors earlier had employed the Greek word in this sense, using it to render shedim "lords, idols" in the Septuagint, and Matt. viii:31 has daimones, translated as deofol in Old English, feend or deuil in Middle English. Another Old English word for this was hellcniht, literally "hell-knight."

The original mythological sense is sometimes written daemon for purposes of distinction. The Demon of Socrates was a daimonion, a "divine principle or inward oracle." His accusers, and later the Church Fathers, however, represented this otherwise. The Demon Star (1895) is Algol.