/wiːk/
[adjective] Lacking physical strength, power, or force; not able to resist pressure or difficulty. It can also describe something that is not convincing, effective, or firm in character.
The word 'weak' was borrowed from Viking invaders, making its very origin an act of linguistic conquest.
The story of 'weak' begins in the Norse-speaking world of Scandinavia. Its immediate source is Old Norse 'veikr', meaning pliant, flexible, or lacking firmness — a word that carried the idea of something that bends rather than holds its ground. This Norse root traces back further to Proto-Germanic 'waikwaz', connected to the idea of yielding, and beyond that to Proto-Indo-European 'weig-' or 'weik-', a root suggesting motion or bending. The earliest sense, then, was not moral or emotional but almost physical — the quality of a green twig that bends in the hand rather than snapping cleanly.
Old Norse 'veikr' crossed the North Sea into England during the Viking Age, roughly the 9th to 11th centuries, when Norsemen settled large parts of northern and eastern England in a region later called the Danelaw. During this period of close contact, hundreds of Norse words filtered into the English spoken by Anglo-Saxon communities. 'Weak' was part of this great wave, eventually appearing in Middle English as 'weik' and later 'weke' in the 13th century. It was, in a sense, a foreign word that never felt foreign — it slotted smoothly into English because the concept it named was already well understood.
Interestingly, Old English had its own words for this idea. 'Wac' (from which we get the modern word 'wake' in some older uses) and 'seoc' both covered aspects of physical frailness or lack of power. But the Norse newcomer proved more durable and versatile. Over time, 'weak' pushed these older terms aside, winning the competition for the same semantic space — a small linguistic victory that reflects the enormous cultural influence the Vikings had on the English language and its speakers.
As centuries passed, 'weak' expanded well beyond its original sense of physical bendiness. By the 14th and 15th centuries, writers were using it to describe weak arguments, weak rulers, and weak character — people who yielded to temptation or pressure in the same way a thin branch yields to wind. This moral dimension became enormously important in religious and philosophical writing, where spiritual weakness was contrasted with the strength of virtue and faith. The word had grown from describing a pliable stick to capturing something deeply human.
The word also gave rise to a productive family of related terms in English. 'Weaken' emerged as a verb, meaning to make or become weak, following a standard English pattern of adding '-en' to adjectives. 'Weakness' appeared as a noun capturing the state or quality of being weak, and 'weakling' — first recorded around the 16th century — added a slightly contemptuous edge, describing a person or creature defined entirely by their lack of strength. Meanwhile, the Old Norse root 'veikr' also contributed to related words in other Germanic languages: German 'weich' (soft, tender) and Dutch 'week' (soft, gentle) are cousins that share the same ancient ancestor and still preserve that earliest sense of something yielding and soft to the touch.