fiendyoudaoicibaDictYouDict
fiend: [OE] Fiend seems originally to have meant ‘hated person’. It was formed in prehistoric times from the past participle of a Germanic verb meaning ‘hate’ (represented in historic times by, for example, Old English fēon, Old High German fiēn, and Gothic fijan). In Old English its meaning had progressed to ‘enemy’ (which is what its German relative feind still means). Then towards the end of the first millennium AD we see evidence of its being applied to the ‘enemy’ of mankind, the Devil. From there it was a short step to an ‘evil spirit’ in general, and hence to any ‘diabolically wicked person’.
hate (v.)youdaoicibaDictYouDict
Old English hatian "regard with extreme ill-will, have a passionate aversion to, treat as an enemy," from Proto-Germanic *haton (cognates: Old Saxon haton, Old Norse hata, German hassen, Gothic hatan "to hate"), from PIE root *kad- "sorrow, hatred" (cognates: Avestan sadra- "grief, sorrow, calamity," Greek kedos "care, trouble, sorrow," Welsh cas "pain, anger"). Related: Hated; hating. French haine (n.), hair (v.) are Germanic. Hate crime attested from 1988.
JobyoudaoicibaDictYouDict
Biblical masc. proper name, from Hebrew Iyyobh, which according to some scholars is literally "hated, persecuted," from ayyabh "he was hostile to," related to ebhah "enmity." Others say it means "the penitent one."
loath (adj.)youdaoicibaDictYouDict
Old English lað "hated; hateful; hostile; repulsive," from Proto-Germanic *laithaz (cognates: Old Saxon, Old Frisian leth "loathsome," Old Norse leiðr "hateful, hostile, loathed;" Middle Dutch lelijc, Dutch leelijk "ugly;" Old High German leid "sorrowful, hateful, offensive, grievous," German Leid "sorrow;" French laid "ugly," from Frankish (Germanic) *laid), from PIE root *leit- "to detest."

Weakened meaning "averse, disinclined" is attested from late 14c. Loath to depart, a line from some long-forgotten song, is recorded since 1580s as a generic term expressive of any tune played at farewells, the sailing of a ship, etc. Related: Loathness.
odium (n.)youdaoicibaDictYouDict
c. 1600, "fact of being hated," from Latin odium "ill-will, hatred, grudge, animosity; offense, offensive conduct," related to odi "I hate" (infinitive odisse), from PIE root *od- "to hate" (cognates: Armenian ateam "I hate," Old Norse atall, Old English atol "dire, horrid, loathsome"). Meaning "hatred, detestation" is from 1650s. Often in an extended form, such as odium theologicum "hatred which is proverbially characteristic of theological disputes" (1670s).