As recalled, there was some kind of contest to come up with a "ship's flag". Someone decided that crew members could submit their ideas; then a ship wide vote would make the final selection. Somebody picked up a can of shoe polish and thought it was as good as any symbol, first four letters of the ship's name too. In fact, I think some folks used KIWI as a nickname for the ship, whether that came before or after the adoption of the KIWI bird for a flag; I have no clue.