Old English freond "one attached to another by feelings of personal regard and preference," from Proto-Germanic *frijōjands "lover, friend" (source also of Old Norse frændi, Old Danish frynt, Old Frisian friund, Dutch vriend, Middle High German friunt, German Freund, Gothic frijonds "friend"), from PIE *priy-ont-, "loving," present-participle form of root *pri- "to love."
Meaning "a Quaker" (a member of the Society of Friends) is from 1670s. Feond ("fiend," originally "enemy") and freond often were paired alliteratively in Old English; both are masculine agent nouns derived from present participle of verbs, but they are not directly related to one another (see fiend). Related: Friends.
in the Facebook sense, attested from 2005, from the noun. Friend occasionally has been used as a verb in English since c. 1200 ("to be friends"), though the more usual verb for "join in friendship, act as a friend" is befriend. Related: Friended; friending. Old English had freonsped "an abundance of friends" (see speed (n.)); freondleast "want of friends;" freondspedig "rich in friends."