Combination of the names 'Zabuza' and 'Haku', a canon-to-some/fanon-to-others yaoi couple from the anime Naruto. Zabuza took Haku in, and raised him to be the ultimate ninja and the ultimate tool. Haku's feelings, whether you want to imply shounen-ai or not, were made glaringly obvious by his unwavering devotion to Zabuza. After all was said and done, though, they *both* really cherished one another.

'ZabuHaku' implies that Zabuza is the dominant partner (as opposed to 'HakuZabu'), but both can be used interchangeably.

When you eat dirt for the first time and leave your family to build a shack in the woods