/bʌlk/
[noun] The large size or heavy weight of something, or the main and largest part of a group or amount. It can also refer to goods that are sold or transported in large quantities without packaging.
Before it meant size, 'bulk' meant a ship's cargo hold — a word born from the belly of a boat.
The word 'bulk' has its roots in the seafaring world of medieval Scandinavia. It comes from the Old Norse word 'bulki', which meant the cargo or load carried inside a ship — specifically, the goods stored in a vessel's hold. This maritime origin makes perfect sense when you picture the great rounded belly of a wooden ship packed tight with goods. Old Norse was the language of the Vikings, and through centuries of Scandinavian trade and settlement in Britain, many of their words found their way into the English language.
The word entered Middle English around the early 15th century, most likely through trade contact between English and Norse or Low German-speaking merchants around the North Sea. Early English usage stuck closely to the nautical sense — 'bulk' referred to a ship's hold or its cargo. Sailors and merchants would speak of goods 'in bulk', meaning unpackaged and loaded loosely into the hold, rather than placed in barrels or crates. This is the direct ancestor of the modern phrase 'in bulk', meaning a large quantity bought all at once.
Over the following two centuries, the word gradually moved away from the ship's hold and onto dry land. As trade language spread into everyday speech, 'bulk' began to be used more generally to describe any large mass or heavy quantity of something. By the 16th and 17th centuries, English writers were using it to talk about the sheer physical size of objects and people, not just cargo. The connection to ships faded, and the word took on the broader meaning of 'large amount' or 'great size' that we know today.
Interestingly, 'bulk' also developed a grammatical life as a verb — 'to bulk up' or 'to bulk out' — meaning to increase in size or to make something larger or heavier. This usage, especially in the context of bodybuilding and physical training, became extremely common in the 20th century. The phrase 'bulking up' captures perfectly how the original sense of something swelling and filling a space — just like cargo filling a hold — lived on in a very different setting.
The word also has close cousins in other Germanic languages. The Old Norse 'bulki' is related to the Old English and Middle Low German word 'balke', meaning a beam or ridge, and both share a deeper root connected to the idea of a rounded, swelling shape. This family of words also gave English the word 'balk' — meaning a large beam of timber, and later a barrier or obstacle — through Old Norse 'bálkr' → Middle English 'balke' → Modern English 'balk'. The shared sense is of something solid, large, and hard to move past, which connects the two words across centuries of meaning.