Noun
butter-box (plural butter-boxes)
(archaic, slang, derogatory, Britain) A Dutch person; used in the era of the Anglo-Dutch Wars.
Continuing north, the 6 km coastal corridor between Dee Why Beach and North Narrabeen is widely considered Sydney’s blue-ribbon surfing belt, with the legendary Long Reef bombora (known locally as "Butter-box") situated smack in the middle. Source: Internet