feud n.

Old English gefea, gefa "foe, enemy, adversary in a blood feud" (the prefix denotes "mutuality"), from adjective fah "at feud, hostile," also "guilty, criminal," from Proto-Germanic *faihaz (source also of Old High German fehan "to hate," Gothic faih "deception"), perhaps from the same PIE source that yielded Sanskrit pisunah "malicious," picacah "demon;" Lithuanian piktas "wicked, angry," peikti "to blame." Weaker sense of "adversary" is first recorded c. 1600.

1610s, "pertaining to feuds," estates of land granted by a superior on condition of services to be rendered to the grantor, from Medieval Latin feudalis, from feudum "feudal estate, land granted to be held as a benefice," of Germanic origin (cognates: Gothic faihu "property," Old High German fihu "cattle;" see fee). Related to Middle English feodary "one who holds lands of an overlord in exchange for service" (late 14c.). Not related to feud.