Friend (dictionary)
one who is affectionately attached to another; pal, buddy; fan, supporter; one who belongs to the same group; one who is not hostile; member of the Religious Society of Friends, Quaker

Consise Oxford Thesaurus
a close friend: COMPANION, boon companion, bosom friend, best friend, intimate, confidante, confidant, familiar, soul mate, alter ego, second self, playmate, playfellow, classmate, schoolmate, workmate; ally, associate; sister, brother; informal pal, chum, sidekick, crony, main man; Brit. informal mate, china, mucker; N. English informal marrow, marra; N. Amer. informal buddy, amigo, compadre, homeboy; archaic compeer.

Etymology
O.E. freond, prp. of freogan "to love, to favor," from P.Gmc. *frijojanan "to love" (cf. O.N. frændi, O.Fris. friund, M.H.G. friunt, Ger. Freund, Goth. frijonds "friend," all alike from prp. forms). Related to O.E. freo "free." Meaning "A Quaker" (a member of the Society of Friends) is from 1679. Feond ("fiend," originally "enemy") and freond, often paired in O.E., both are masculine agent nouns derived from prp. of verbs, but are not directly related to one another.

droog
"gang member, young ruffian," a transliteration of the Rus. word for "friend," introduced by Eng. novelist Anthony Burgess in "A Clockwork Orange" (1962). The Rus. word comes from O.C.S. drugu "companion, friend, other" (cf. Boh. drug "companion," Serbo-Cr. drugi "other"), which belongs to a group of related IE words (cf. Lith. draugas "friend, traveling companion;" Goth. driugan "do military service," ga-drauhts "soldier;" O.N. drott, O.E. dryht, O.H.G. truht "multitude, people, army") whose original sense seems to be "companio18:36 3/02/200818:36 3/02/2008n."

amigo
"friend, comrade," often a form of address, 1837, Amer.Eng. (first attested in the phrase adios, Amigo), from Sp., lit. "friend," from L. amicus.