Old English freond "friend," present participle of freogan "to love, to favor," from Proto-Germanic *frijojanan "to love" (cf. Old Norse frændi, Old Frisian friund, Middle High German friunt, German Freund, Gothic frijonds "friend," all alike from present participle forms). Related to Old English freo "free" (see free (adj.)).
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 are not directly related to one another (see fiend). Related: Friends.
in the Facebook sense, attested from 2005, from the noun, but friend has been used as a verb in English since late 14c. Related: Friended; friending. Old English had freonsped "an abundance of friends" (see speed (n.)); freondleast "want of friends;" freondspedig "rich in friends", all of which would be useful now.
Relationship between classes in the language C++.