The history of Kohukohu
begins with a visit from Kupe on his return voyage to Hawaiiki. Angry at the food from the hangi being insufficiently cooked, he cursed those responsible using the word kohu. Hence Kohukohu.
The word kohu also has two other meanings - "misty" and "basin".
As misty mornings promise a lovely day in the Hokianga, this may be the preferred meaning. Take your choice!