No borrowing is established. German Feind continues Old and Middle High German forms; English fiend independently continues Old English fēond. Both branches meet at reconstructed *fi(j)and-.

No. German Feind remains an ordinary enemy noun, English fiend foregrounds demon and vicious-person senses, and Old Norse is glossed enemy or devil. Shared ancestry does not erase branch-specific semantics.

No. OED records enemy or foe from Old English to 1450 and explains the Devil as a specific use of enemy as the ultimate adversary.

No. English fiend continues Old English fēond; Gothic fijands is a collateral Germanic cousin. Both meet at reconstructed *fi(j)and-.

No borrowing is established. OED and the Middle English Dictionary both derive the medieval forms from Old English fēond or fīond.

No. OED reports coexisting long and short vowels in Middle and early modern English and says the long vowel became dominant by the eighteenth century.

No. OED calls friend an antonym with a similar agent-noun formation. Similar morphology does not establish one lexical root.

No. Enemy or foe remains recorded into the fifteenth century while Devil, demon, monster, and other senses coexist through the Middle English record.

No. OED invokes Hebrew śāṭān, adversary, to explain the conceptual and translation background of the Devil-as-Enemy use; it does not derive the English word from Hebrew.

No. OED marks the literal enemy or foe sense obsolete and dates that sense through 1450, while supernatural and hostile-person senses continue.

No. OED says fiend shows a similar formation, but the two agent nouns are built on different verb bases. Parallel morphology does not establish cognacy.

Not as a simple word-to-word descent. Fiend continues Old English fēond, the lexicalized Germanic one-who-hates formation; fēogan continues the related verb base.

No. Bosworth–Toller gives enemy, foe, and Devil, while OED separates literal enemy, the Devil, demons, and malevolent-person uses already present in Old English.

No. English fiend continues Old English fēond; Gothic fijands is a collateral Germanic cousin. Both meet at the reconstructed *fi(j)and- formation.

No. OED classifies it as a strong masculine agent noun originally in the nd-class, and cross-Germanic evidence places lexicalization before Old English. Its participial origin remains historically visible without erasing noun status.

No. OED explains unmutated dialect forms and i-mutated inflectional forms inside one inherited paradigm, with later analogical remodeling.

No. OED dates enemy or foe from Old English to 1450 and marks it obsolete; Devil was originally a specific use of enemy as the ultimate adversary.

OED explains the Devil as the original or ultimate enemy, early translating Latin hostis and ultimately reflecting the literal adversary sense of Hebrew satan. This is a semantic and translation history, not proof of one coinage event.

No. OED records endingless i-mutated and unmutated plurals, re-formed fēondas or fīondas, and occasional weak forms.

No. OED says friend is an antonym with a similar agent-noun formation. Similar morphology does not establish one lexical root or cognate pair.