It may have originally been mostly biconsonantal, to which various affixes (such as verbal extensions) were then added and lexicalized.
ɪt mˌeɪhɐv ɚɹˈɪdʒɪnəli bˌɪn mˈoʊstli baɪkˈɑːnsənˌæntəl, tə wˌɪtʃ vˈɛɹiəs ɐfˈɪksᵻz sˈʌtʃ ɐz vˈɜːbəl ɛkstˈɛnʃənz wɜː ðˈɛn ˈædᵻd ænd lˈɛksɪkəlˌaɪzd.