O.E.
feond "enemy, foe," originally prp. of
feogan "to hate," from P.Gmc.
*fijæjan (cf. O.N.
fjandi, O.H.G.
fiant, Goth.
fijands, like the O.E. word all prp. forms), from PIE base
*pei-/*pi- "to blame, revile" (cf. Goth.
faian "to blame;" see
passion). As spelling suggests, it was originally the opposite of
friend, but the word began to be used in O.E. for "Satan" (as the "enemy of mankind"), which shifted its sense to "diabolical person" (c.1220). The old sense of the word devolved to
foe, then to the borrowed
enemy. For spelling with
-ie- see
field. Meaning "devotee (of whatever is indicated)," cf.
dope fiend, is from 1865.
[feend] 
