means The underground part of a plant that anchors it and draws up water and nutrients — and, by extension, the source or origin of anything.

from From Old English 'rōt,' itself borrowed from Old Norse 'rót,' both reaching back to a Proto-Germanic source and ultimately a Proto-Indo-European root meaning 'to grow' — making it a distant cousin of Latin 'radix' (whence 'radish' and 'radical'). The figurative sense of 'origin' or 'source' is ancient: the idea that everything visible grows from something hidden below is older than the word itself.