fiendly

From Middle English feendly, fendly (“hostile, devilish”), from Old English fēondliċ (“hostile”), corresponding to fiend +‎ -ly. Cognate with Dutch vijandelijk (“hostile”), German feindlich (“hostile”), Danish fjendtlig (“hostile”), Swedish fiendtlig, fientlig (“hostile”).

fiendly (comparative more fiendly, superlative most fiendly)

1. (obsolete) Hostile.
2. (now rare) Like a fiend; devilish.
   • 1485, Sir Thomas Malory, chapter primum, in Le Morte Darthur, book XI:

     Soo whanne sir Laūcelot came thydder / he sawe wryten vpon the tombe letters of gold that said thus / Here shalle come a lybard of kynges blood / and he shalle slee this serpent / […] / Soo thenne sir launcelot lyfte vp the tombe / and there came out an horryble & a fyendly dragon spyttynge fyre oute of his mouthe

• Findley