The plural is kahuna.

You are almost correct.

Kahuna (is one hahuna)
KAhuna (where the first A is emphasized is the plural form)

The Hawai'ians had an oral tradition with no written language before the (Christian) missionaries arrived in Hawai'i in 1820.

I guess you could call me the big kahuna. I have been studying Hawai'ian culture and mysticism for several years, and use Hawai'ian energetic healing technology.