Although this may seem like a truism, friend derives, as says Danilo Enrique companion, amicus - i, Latin noun whose deaf consonant is large on their way to the Spanish, the same thing happened in formica, Ant or ficus, fig. Also amicus derives from the lexeme am - master - as - are, love, love and the suffix adjetivante and sustantivante - icus. The meaning is obvious, as also the partner says.