rōt

Old Norse rót replaced the native Old English word wyrt during the Viking settlement of England in the ninth and tenth centuries. This is unusual: plant words tend to be conservative, staying in a language for millennia. But the Vikings were so thoroughly integrated into northern English communities that their word for root displaced the English one. Wyrt did not vanish entirely — it survives in 'wort' (a plant used in brewing or medicine) and in the suffix '-wort' in plant names like liverwort, mugwort, and St. John's wort. But for the underground part of a plant, Norse won.

The metaphorical uses of root are as old as the physical one. The 'root of a problem,' 'putting down roots,' and 'rooting for' something all treat the underground anchor of a plant as a metaphor for origin, stability, or support. In mathematics, the 'root' of a number (square root, cube root) uses the same metaphor: the hidden value from which the visible number grows. In linguistics, the 'root' of a word is the smallest meaningful element — the buried core from which all forms grow.

Mangrove roots grow above water, forming visible arched structures. Banyan tree roots drop from branches and grow downward, creating new trunks — a single banyan can cover several acres. The Great Banyan in Kolkata's Acharya Jagadish Chandra Bose Indian Botanic Garden has a canopy circumference of 330 meters and looks like a forest but is one tree. Roots are not always underground. They are not always invisible. But the word root carries the assumption of hiddenness — the unseen support, the buried origin.

The computing term 'root' — as in root access, root directory, root user — is the most recent metaphorical extension. The root user has access to everything because they are at the base of the system. The root directory contains all other directories. The Norse word for the underground part of a plant is now the foundation of every Unix-based operating system.