For that matter, why not 'fanetik'? There is no phonetic rule. English spellings are a matter of word history and historical usage.
elephant: c.1300, olyfaunt, from O.Fr. oliphant, from L. elephantus, from Gk. elephas (gen. elephantos) "elephant, ivory," probably from a non-I.E. language, likely via Phoenician (cf. Hamitic elu "elephant," source of the word for it in many